| /* |
| * linux/fs/namespace.c |
| * |
| * (C) Copyright Al Viro 2000, 2001 |
| * Released under GPL v2. |
| * |
| * Based on code from fs/super.c, copyright Linus Torvalds and others. |
| * Heavily rewritten. |
| */ |
| |
| #include <linux/syscalls.h> |
| #include <linux/export.h> |
| #include <linux/capability.h> |
| #include <linux/mnt_namespace.h> |
| #include <linux/user_namespace.h> |
| #include <linux/namei.h> |
| #include <linux/security.h> |
| #include <linux/idr.h> |
| #include <linux/acct.h> /* acct_auto_close_mnt */ |
| #include <linux/ramfs.h> /* init_rootfs */ |
| #include <linux/fs_struct.h> /* get_fs_root et.al. */ |
| #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ |
| #include <linux/uaccess.h> |
| #include <linux/proc_fs.h> |
| #include "pnode.h" |
| #include "internal.h" |
| |
| #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) |
| #define HASH_SIZE (1UL << HASH_SHIFT) |
| |
| static int event; |
| static DEFINE_IDA(mnt_id_ida); |
| static DEFINE_IDA(mnt_group_ida); |
| static DEFINE_SPINLOCK(mnt_id_lock); |
| static int mnt_id_start = 0; |
| static int mnt_group_start = 1; |
| |
| static struct list_head *mount_hashtable __read_mostly; |
| static struct kmem_cache *mnt_cache __read_mostly; |
| static struct rw_semaphore namespace_sem; |
| |
| /* /sys/fs */ |
| struct kobject *fs_kobj; |
| EXPORT_SYMBOL_GPL(fs_kobj); |
| |
| /* |
| * vfsmount lock may be taken for read to prevent changes to the |
| * vfsmount hash, ie. during mountpoint lookups or walking back |
| * up the tree. |
| * |
| * It should be taken for write in all cases where the vfsmount |
| * tree or hash is modified or when a vfsmount structure is modified. |
| */ |
| DEFINE_BRLOCK(vfsmount_lock); |
| |
| static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) |
| { |
| unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); |
| tmp += ((unsigned long)dentry / L1_CACHE_BYTES); |
| tmp = tmp + (tmp >> HASH_SHIFT); |
| return tmp & (HASH_SIZE - 1); |
| } |
| |
| #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) |
| |
| /* |
| * allocation is serialized by namespace_sem, but we need the spinlock to |
| * serialize with freeing. |
| */ |
| static int mnt_alloc_id(struct mount *mnt) |
| { |
| int res; |
| |
| retry: |
| ida_pre_get(&mnt_id_ida, GFP_KERNEL); |
| spin_lock(&mnt_id_lock); |
| res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); |
| if (!res) |
| mnt_id_start = mnt->mnt_id + 1; |
| spin_unlock(&mnt_id_lock); |
| if (res == -EAGAIN) |
| goto retry; |
| |
| return res; |
| } |
| |
| static void mnt_free_id(struct mount *mnt) |
| { |
| int id = mnt->mnt_id; |
| spin_lock(&mnt_id_lock); |
| ida_remove(&mnt_id_ida, id); |
| if (mnt_id_start > id) |
| mnt_id_start = id; |
| spin_unlock(&mnt_id_lock); |
| } |
| |
| /* |
| * Allocate a new peer group ID |
| * |
| * mnt_group_ida is protected by namespace_sem |
| */ |
| static int mnt_alloc_group_id(struct mount *mnt) |
| { |
| int res; |
| |
| if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) |
| return -ENOMEM; |
| |
| res = ida_get_new_above(&mnt_group_ida, |
| mnt_group_start, |
| &mnt->mnt_group_id); |
| if (!res) |
| mnt_group_start = mnt->mnt_group_id + 1; |
| |
| return res; |
| } |
| |
| /* |
| * Release a peer group ID |
| */ |
| void mnt_release_group_id(struct mount *mnt) |
| { |
| int id = mnt->mnt_group_id; |
| ida_remove(&mnt_group_ida, id); |
| if (mnt_group_start > id) |
| mnt_group_start = id; |
| mnt->mnt_group_id = 0; |
| } |
| |
| /* |
| * vfsmount lock must be held for read |
| */ |
| static inline void mnt_add_count(struct mount *mnt, int n) |
| { |
| #ifdef CONFIG_SMP |
| this_cpu_add(mnt->mnt_pcp->mnt_count, n); |
| #else |
| preempt_disable(); |
| mnt->mnt_count += n; |
| preempt_enable(); |
| #endif |
| } |
| |
| /* |
| * vfsmount lock must be held for write |
| */ |
| unsigned int mnt_get_count(struct mount *mnt) |
| { |
| #ifdef CONFIG_SMP |
| unsigned int count = 0; |
| int cpu; |
| |
| for_each_possible_cpu(cpu) { |
| count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; |
| } |
| |
| return count; |
| #else |
| return mnt->mnt_count; |
| #endif |
| } |
| |
| static struct mount *alloc_vfsmnt(const char *name) |
| { |
| struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); |
| if (mnt) { |
| int err; |
| |
| err = mnt_alloc_id(mnt); |
| if (err) |
| goto out_free_cache; |
| |
| if (name) { |
| mnt->mnt_devname = kstrdup(name, GFP_KERNEL); |
| if (!mnt->mnt_devname) |
| goto out_free_id; |
| } |
| |
| #ifdef CONFIG_SMP |
| mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); |
| if (!mnt->mnt_pcp) |
| goto out_free_devname; |
| |
| this_cpu_add(mnt->mnt_pcp->mnt_count, 1); |
| #else |
| mnt->mnt_count = 1; |
| mnt->mnt_writers = 0; |
| #endif |
| |
| INIT_LIST_HEAD(&mnt->mnt_hash); |
| INIT_LIST_HEAD(&mnt->mnt_child); |
| INIT_LIST_HEAD(&mnt->mnt_mounts); |
| INIT_LIST_HEAD(&mnt->mnt_list); |
| INIT_LIST_HEAD(&mnt->mnt_expire); |
| INIT_LIST_HEAD(&mnt->mnt_share); |
| INIT_LIST_HEAD(&mnt->mnt_slave_list); |
| INIT_LIST_HEAD(&mnt->mnt_slave); |
| #ifdef CONFIG_FSNOTIFY |
| INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); |
| #endif |
| } |
| return mnt; |
| |
| #ifdef CONFIG_SMP |
| out_free_devname: |
| kfree(mnt->mnt_devname); |
| #endif |
| out_free_id: |
| mnt_free_id(mnt); |
| out_free_cache: |
| kmem_cache_free(mnt_cache, mnt); |
| return NULL; |
| } |
| |
| /* |
| * Most r/o checks on a fs are for operations that take |
| * discrete amounts of time, like a write() or unlink(). |
| * We must keep track of when those operations start |
| * (for permission checks) and when they end, so that |
| * we can determine when writes are able to occur to |
| * a filesystem. |
| */ |
| /* |
| * __mnt_is_readonly: check whether a mount is read-only |
| * @mnt: the mount to check for its write status |
| * |
| * This shouldn't be used directly ouside of the VFS. |
| * It does not guarantee that the filesystem will stay |
| * r/w, just that it is right *now*. This can not and |
| * should not be used in place of IS_RDONLY(inode). |
| * mnt_want/drop_write() will _keep_ the filesystem |
| * r/w. |
| */ |
| int __mnt_is_readonly(struct vfsmount *mnt) |
| { |
| if (mnt->mnt_flags & MNT_READONLY) |
| return 1; |
| if (mnt->mnt_sb->s_flags & MS_RDONLY) |
| return 1; |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(__mnt_is_readonly); |
| |
| static inline void mnt_inc_writers(struct mount *mnt) |
| { |
| #ifdef CONFIG_SMP |
| this_cpu_inc(mnt->mnt_pcp->mnt_writers); |
| #else |
| mnt->mnt_writers++; |
| #endif |
| } |
| |
| static inline void mnt_dec_writers(struct mount *mnt) |
| { |
| #ifdef CONFIG_SMP |
| this_cpu_dec(mnt->mnt_pcp->mnt_writers); |
| #else |
| mnt->mnt_writers--; |
| #endif |
| } |
| |
| static unsigned int mnt_get_writers(struct mount *mnt) |
| { |
| #ifdef CONFIG_SMP |
| unsigned int count = 0; |
| int cpu; |
| |
| for_each_possible_cpu(cpu) { |
| count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; |
| } |
| |
| return count; |
| #else |
| return mnt->mnt_writers; |
| #endif |
| } |
| |
| static int mnt_is_readonly(struct vfsmount *mnt) |
| { |
| if (mnt->mnt_sb->s_readonly_remount) |
| return 1; |
| /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ |
| smp_rmb(); |
| return __mnt_is_readonly(mnt); |
| } |
| |
| /* |
| * Most r/o checks on a fs are for operations that take |
| * discrete amounts of time, like a write() or unlink(). |
| * We must keep track of when those operations start |
| * (for permission checks) and when they end, so that |
| * we can determine when writes are able to occur to |
| * a filesystem. |
| */ |
| /** |
| * mnt_want_write - get write access to a mount |
| * @m: the mount on which to take a write |
| * |
| * This tells the low-level filesystem that a write is |
| * about to be performed to it, and makes sure that |
| * writes are allowed before returning success. When |
| * the write operation is finished, mnt_drop_write() |
| * must be called. This is effectively a refcount. |
| */ |
| int mnt_want_write(struct vfsmount *m) |
| { |
| struct mount *mnt = real_mount(m); |
| int ret = 0; |
| |
| preempt_disable(); |
| mnt_inc_writers(mnt); |
| /* |
| * The store to mnt_inc_writers must be visible before we pass |
| * MNT_WRITE_HOLD loop below, so that the slowpath can see our |
| * incremented count after it has set MNT_WRITE_HOLD. |
| */ |
| smp_mb(); |
| while (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) |
| cpu_relax(); |
| /* |
| * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will |
| * be set to match its requirements. So we must not load that until |
| * MNT_WRITE_HOLD is cleared. |
| */ |
| smp_rmb(); |
| if (mnt_is_readonly(m)) { |
| mnt_dec_writers(mnt); |
| ret = -EROFS; |
| } |
| preempt_enable(); |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(mnt_want_write); |
| |
| /** |
| * mnt_clone_write - get write access to a mount |
| * @mnt: the mount on which to take a write |
| * |
| * This is effectively like mnt_want_write, except |
| * it must only be used to take an extra write reference |
| * on a mountpoint that we already know has a write reference |
| * on it. This allows some optimisation. |
| * |
| * After finished, mnt_drop_write must be called as usual to |
| * drop the reference. |
| */ |
| int mnt_clone_write(struct vfsmount *mnt) |
| { |
| /* superblock may be r/o */ |
| if (__mnt_is_readonly(mnt)) |
| return -EROFS; |
| preempt_disable(); |
| mnt_inc_writers(real_mount(mnt)); |
| preempt_enable(); |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(mnt_clone_write); |
| |
| /** |
| * mnt_want_write_file - get write access to a file's mount |
| * @file: the file who's mount on which to take a write |
| * |
| * This is like mnt_want_write, but it takes a file and can |
| * do some optimisations if the file is open for write already |
| */ |
| int mnt_want_write_file(struct file *file) |
| { |
| struct inode *inode = file->f_dentry->d_inode; |
| if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) |
| return mnt_want_write(file->f_path.mnt); |
| else |
| return mnt_clone_write(file->f_path.mnt); |
| } |
| EXPORT_SYMBOL_GPL(mnt_want_write_file); |
| |
| /** |
| * mnt_drop_write - give up write access to a mount |
| * @mnt: the mount on which to give up write access |
| * |
| * Tells the low-level filesystem that we are done |
| * performing writes to it. Must be matched with |
| * mnt_want_write() call above. |
| */ |
| void mnt_drop_write(struct vfsmount *mnt) |
| { |
| preempt_disable(); |
| mnt_dec_writers(real_mount(mnt)); |
| preempt_enable(); |
| } |
| EXPORT_SYMBOL_GPL(mnt_drop_write); |
| |
| void mnt_drop_write_file(struct file *file) |
| { |
| mnt_drop_write(file->f_path.mnt); |
| } |
| EXPORT_SYMBOL(mnt_drop_write_file); |
| |
| static int mnt_make_readonly(struct mount *mnt) |
| { |
| int ret = 0; |
| |
| br_write_lock(&vfsmount_lock); |
| mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; |
| /* |
| * After storing MNT_WRITE_HOLD, we'll read the counters. This store |
| * should be visible before we do. |
| */ |
| smp_mb(); |
| |
| /* |
| * With writers on hold, if this value is zero, then there are |
| * definitely no active writers (although held writers may subsequently |
| * increment the count, they'll have to wait, and decrement it after |
| * seeing MNT_READONLY). |
| * |
| * It is OK to have counter incremented on one CPU and decremented on |
| * another: the sum will add up correctly. The danger would be when we |
| * sum up each counter, if we read a counter before it is incremented, |
| * but then read another CPU's count which it has been subsequently |
| * decremented from -- we would see more decrements than we should. |
| * MNT_WRITE_HOLD protects against this scenario, because |
| * mnt_want_write first increments count, then smp_mb, then spins on |
| * MNT_WRITE_HOLD, so it can't be decremented by another CPU while |
| * we're counting up here. |
| */ |
| if (mnt_get_writers(mnt) > 0) |
| ret = -EBUSY; |
| else |
| mnt->mnt.mnt_flags |= MNT_READONLY; |
| /* |
| * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers |
| * that become unheld will see MNT_READONLY. |
| */ |
| smp_wmb(); |
| mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |
| br_write_unlock(&vfsmount_lock); |
| return ret; |
| } |
| |
| static void __mnt_unmake_readonly(struct mount *mnt) |
| { |
| br_write_lock(&vfsmount_lock); |
| mnt->mnt.mnt_flags &= ~MNT_READONLY; |
| br_write_unlock(&vfsmount_lock); |
| } |
| |
| int sb_prepare_remount_readonly(struct super_block *sb) |
| { |
| struct mount *mnt; |
| int err = 0; |
| |
| /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ |
| if (atomic_long_read(&sb->s_remove_count)) |
| return -EBUSY; |
| |
| br_write_lock(&vfsmount_lock); |
| list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { |
| if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { |
| mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; |
| smp_mb(); |
| if (mnt_get_writers(mnt) > 0) { |
| err = -EBUSY; |
| break; |
| } |
| } |
| } |
| if (!err && atomic_long_read(&sb->s_remove_count)) |
| err = -EBUSY; |
| |
| if (!err) { |
| sb->s_readonly_remount = 1; |
| smp_wmb(); |
| } |
| list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { |
| if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) |
| mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |
| } |
| br_write_unlock(&vfsmount_lock); |
| |
| return err; |
| } |
| |
| static void free_vfsmnt(struct mount *mnt) |
| { |
| kfree(mnt->mnt.data); |
| kfree(mnt->mnt_devname); |
| mnt_free_id(mnt); |
| #ifdef CONFIG_SMP |
| free_percpu(mnt->mnt_pcp); |
| #endif |
| kmem_cache_free(mnt_cache, mnt); |
| } |
| |
| /* |
| * find the first or last mount at @dentry on vfsmount @mnt depending on |
| * @dir. If @dir is set return the first mount else return the last mount. |
| * vfsmount_lock must be held for read or write. |
| */ |
| struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, |
| int dir) |
| { |
| struct list_head *head = mount_hashtable + hash(mnt, dentry); |
| struct list_head *tmp = head; |
| struct mount *p, *found = NULL; |
| |
| for (;;) { |
| tmp = dir ? tmp->next : tmp->prev; |
| p = NULL; |
| if (tmp == head) |
| break; |
| p = list_entry(tmp, struct mount, mnt_hash); |
| if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) { |
| found = p; |
| break; |
| } |
| } |
| return found; |
| } |
| |
| /* |
| * lookup_mnt - Return the first child mount mounted at path |
| * |
| * "First" means first mounted chronologically. If you create the |
| * following mounts: |
| * |
| * mount /dev/sda1 /mnt |
| * mount /dev/sda2 /mnt |
| * mount /dev/sda3 /mnt |
| * |
| * Then lookup_mnt() on the base /mnt dentry in the root mount will |
| * return successively the root dentry and vfsmount of /dev/sda1, then |
| * /dev/sda2, then /dev/sda3, then NULL. |
| * |
| * lookup_mnt takes a reference to the found vfsmount. |
| */ |
| struct vfsmount *lookup_mnt(struct path *path) |
| { |
| struct mount *child_mnt; |
| |
| br_read_lock(&vfsmount_lock); |
| child_mnt = __lookup_mnt(path->mnt, path->dentry, 1); |
| if (child_mnt) { |
| mnt_add_count(child_mnt, 1); |
| br_read_unlock(&vfsmount_lock); |
| return &child_mnt->mnt; |
| } else { |
| br_read_unlock(&vfsmount_lock); |
| return NULL; |
| } |
| } |
| |
| static inline int check_mnt(struct mount *mnt) |
| { |
| return mnt->mnt_ns == current->nsproxy->mnt_ns; |
| } |
| |
| /* |
| * vfsmount lock must be held for write |
| */ |
| static void touch_mnt_namespace(struct mnt_namespace *ns) |
| { |
| if (ns) { |
| ns->event = ++event; |
| wake_up_interruptible(&ns->poll); |
| } |
| } |
| |
| /* |
| * vfsmount lock must be held for write |
| */ |
| static void __touch_mnt_namespace(struct mnt_namespace *ns) |
| { |
| if (ns && ns->event != event) { |
| ns->event = event; |
| wake_up_interruptible(&ns->poll); |
| } |
| } |
| |
| /* |
| * Clear dentry's mounted state if it has no remaining mounts. |
| * vfsmount_lock must be held for write. |
| */ |
| static void dentry_reset_mounted(struct dentry *dentry) |
| { |
| unsigned u; |
| |
| for (u = 0; u < HASH_SIZE; u++) { |
| struct mount *p; |
| |
| list_for_each_entry(p, &mount_hashtable[u], mnt_hash) { |
| if (p->mnt_mountpoint == dentry) |
| return; |
| } |
| } |
| spin_lock(&dentry->d_lock); |
| dentry->d_flags &= ~DCACHE_MOUNTED; |
| spin_unlock(&dentry->d_lock); |
| } |
| |
| /* |
| * vfsmount lock must be held for write |
| */ |
| static void detach_mnt(struct mount *mnt, struct path *old_path) |
| { |
| old_path->dentry = mnt->mnt_mountpoint; |
| old_path->mnt = &mnt->mnt_parent->mnt; |
| mnt->mnt_parent = mnt; |
| mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
| list_del_init(&mnt->mnt_child); |
| list_del_init(&mnt->mnt_hash); |
| dentry_reset_mounted(old_path->dentry); |
| } |
| |
| /* |
| * vfsmount lock must be held for write |
| */ |
| void mnt_set_mountpoint(struct mount *mnt, struct dentry *dentry, |
| struct mount *child_mnt) |
| { |
| mnt_add_count(mnt, 1); /* essentially, that's mntget */ |
| child_mnt->mnt_mountpoint = dget(dentry); |
| child_mnt->mnt_parent = mnt; |
| spin_lock(&dentry->d_lock); |
| dentry->d_flags |= DCACHE_MOUNTED; |
| spin_unlock(&dentry->d_lock); |
| } |
| |
| /* |
| * vfsmount lock must be held for write |
| */ |
| static void attach_mnt(struct mount *mnt, struct path *path) |
| { |
| mnt_set_mountpoint(real_mount(path->mnt), path->dentry, mnt); |
| list_add_tail(&mnt->mnt_hash, mount_hashtable + |
| hash(path->mnt, path->dentry)); |
| list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts); |
| } |
| |
| /* |
| * vfsmount lock must be held for write |
| */ |
| static void commit_tree(struct mount *mnt) |
| { |
| struct mount *parent = mnt->mnt_parent; |
| struct mount *m; |
| LIST_HEAD(head); |
| struct mnt_namespace *n = parent->mnt_ns; |
| |
| BUG_ON(parent == mnt); |
| |
| list_add_tail(&head, &mnt->mnt_list); |
| list_for_each_entry(m, &head, mnt_list) |
| m->mnt_ns = n; |
| |
| list_splice(&head, n->list.prev); |
| |
| list_add_tail(&mnt->mnt_hash, mount_hashtable + |
| hash(&parent->mnt, mnt->mnt_mountpoint)); |
| list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
| touch_mnt_namespace(n); |
| } |
| |
| static struct mount *next_mnt(struct mount *p, struct mount *root) |
| { |
| struct list_head *next = p->mnt_mounts.next; |
| if (next == &p->mnt_mounts) { |
| while (1) { |
| if (p == root) |
| return NULL; |
| next = p->mnt_child.next; |
| if (next != &p->mnt_parent->mnt_mounts) |
| break; |
| p = p->mnt_parent; |
| } |
| } |
| return list_entry(next, struct mount, mnt_child); |
| } |
| |
| static struct mount *skip_mnt_tree(struct mount *p) |
| { |
| struct list_head *prev = p->mnt_mounts.prev; |
| while (prev != &p->mnt_mounts) { |
| p = list_entry(prev, struct mount, mnt_child); |
| prev = p->mnt_mounts.prev; |
| } |
| return p; |
| } |
| |
| struct vfsmount * |
| vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) |
| { |
| struct mount *mnt; |
| struct dentry *root; |
| |
| if (!type) |
| return ERR_PTR(-ENODEV); |
| |
| mnt = alloc_vfsmnt(name); |
| if (!mnt) |
| return ERR_PTR(-ENOMEM); |
| |
| mnt->mnt.data = NULL; |
| if (type->alloc_mnt_data) { |
| mnt->mnt.data = type->alloc_mnt_data(); |
| if (!mnt->mnt.data) { |
| mnt_free_id(mnt); |
| free_vfsmnt(mnt); |
| return ERR_PTR(-ENOMEM); |
| } |
| } |
| if (flags & MS_KERNMOUNT) |
| mnt->mnt.mnt_flags = MNT_INTERNAL; |
| |
| root = mount_fs(type, flags, name, &mnt->mnt, data); |
| if (IS_ERR(root)) { |
| kfree(mnt->mnt.data); |
| free_vfsmnt(mnt); |
| return ERR_CAST(root); |
| } |
| |
| mnt->mnt.mnt_root = root; |
| mnt->mnt.mnt_sb = root->d_sb; |
| mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
| mnt->mnt_parent = mnt; |
| br_write_lock(&vfsmount_lock); |
| list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts); |
| br_write_unlock(&vfsmount_lock); |
| return &mnt->mnt; |
| } |
| EXPORT_SYMBOL_GPL(vfs_kern_mount); |
| |
| static struct mount *clone_mnt(struct mount *old, struct dentry *root, |
| int flag) |
| { |
| struct super_block *sb = old->mnt.mnt_sb; |
| struct mount *mnt; |
| int err; |
| |
| mnt = alloc_vfsmnt(old->mnt_devname); |
| if (!mnt) |
| return ERR_PTR(-ENOMEM); |
| |
| if (sb->s_op->clone_mnt_data) { |
| mnt->mnt.data = sb->s_op->clone_mnt_data(old->mnt.data); |
| if (!mnt->mnt.data) { |
| goto out_free; |
| } |
| } |
| |
| if (flag & (CL_SLAVE | CL_PRIVATE)) |
| mnt->mnt_group_id = 0; /* not a peer of original */ |
| else |
| mnt->mnt_group_id = old->mnt_group_id; |
| |
| if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { |
| err = mnt_alloc_group_id(mnt); |
| if (err) |
| goto out_free; |
| } |
| |
| mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD; |
| atomic_inc(&sb->s_active); |
| mnt->mnt.mnt_sb = sb; |
| mnt->mnt.mnt_root = dget(root); |
| mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
| mnt->mnt_parent = mnt; |
| br_write_lock(&vfsmount_lock); |
| list_add_tail(&mnt->mnt_instance, &sb->s_mounts); |
| br_write_unlock(&vfsmount_lock); |
| |
| if (flag & CL_SLAVE) { |
| list_add(&mnt->mnt_slave, &old->mnt_slave_list); |
| mnt->mnt_master = old; |
| CLEAR_MNT_SHARED(mnt); |
| } else if (!(flag & CL_PRIVATE)) { |
| if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) |
| list_add(&mnt->mnt_share, &old->mnt_share); |
| if (IS_MNT_SLAVE(old)) |
| list_add(&mnt->mnt_slave, &old->mnt_slave); |
| mnt->mnt_master = old->mnt_master; |
| } |
| if (flag & CL_MAKE_SHARED) |
| set_mnt_shared(mnt); |
| |
| /* stick the duplicate mount on the same expiry list |
| * as the original if that was on one */ |
| if (flag & CL_EXPIRE) { |
| if (!list_empty(&old->mnt_expire)) |
| list_add(&mnt->mnt_expire, &old->mnt_expire); |
| } |
| |
| return mnt; |
| |
| out_free: |
| kfree(mnt->mnt.data); |
| free_vfsmnt(mnt); |
| return ERR_PTR(err); |
| } |
| |
| static inline void mntfree(struct mount *mnt) |
| { |
| struct vfsmount *m = &mnt->mnt; |
| struct super_block *sb = m->mnt_sb; |
| |
| /* |
| * This probably indicates that somebody messed |
| * up a mnt_want/drop_write() pair. If this |
| * happens, the filesystem was probably unable |
| * to make r/w->r/o transitions. |
| */ |
| /* |
| * The locking used to deal with mnt_count decrement provides barriers, |
| * so mnt_get_writers() below is safe. |
| */ |
| WARN_ON(mnt_get_writers(mnt)); |
| fsnotify_vfsmount_delete(m); |
| dput(m->mnt_root); |
| free_vfsmnt(mnt); |
| deactivate_super(sb); |
| } |
| |
| static void mntput_no_expire(struct mount *mnt) |
| { |
| put_again: |
| #ifdef CONFIG_SMP |
| br_read_lock(&vfsmount_lock); |
| if (likely(mnt->mnt_ns)) { |
| /* shouldn't be the last one */ |
| mnt_add_count(mnt, -1); |
| br_read_unlock(&vfsmount_lock); |
| return; |
| } |
| br_read_unlock(&vfsmount_lock); |
| |
| br_write_lock(&vfsmount_lock); |
| mnt_add_count(mnt, -1); |
| if (mnt_get_count(mnt)) { |
| br_write_unlock(&vfsmount_lock); |
| return; |
| } |
| #else |
| mnt_add_count(mnt, -1); |
| if (likely(mnt_get_count(mnt))) |
| return; |
| br_write_lock(&vfsmount_lock); |
| #endif |
| if (unlikely(mnt->mnt_pinned)) { |
| mnt_add_count(mnt, mnt->mnt_pinned + 1); |
| mnt->mnt_pinned = 0; |
| br_write_unlock(&vfsmount_lock); |
| acct_auto_close_mnt(&mnt->mnt); |
| goto put_again; |
| } |
| |
| list_del(&mnt->mnt_instance); |
| br_write_unlock(&vfsmount_lock); |
| mntfree(mnt); |
| } |
| |
| void mntput(struct vfsmount *mnt) |
| { |
| if (mnt) { |
| struct mount *m = real_mount(mnt); |
| /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ |
| if (unlikely(m->mnt_expiry_mark)) |
| m->mnt_expiry_mark = 0; |
| mntput_no_expire(m); |
| } |
| } |
| EXPORT_SYMBOL(mntput); |
| |
| struct vfsmount *mntget(struct vfsmount *mnt) |
| { |
| if (mnt) |
| mnt_add_count(real_mount(mnt), 1); |
| return mnt; |
| } |
| EXPORT_SYMBOL(mntget); |
| |
| void mnt_pin(struct vfsmount *mnt) |
| { |
| br_write_lock(&vfsmount_lock); |
| real_mount(mnt)->mnt_pinned++; |
| br_write_unlock(&vfsmount_lock); |
| } |
| EXPORT_SYMBOL(mnt_pin); |
| |
| void mnt_unpin(struct vfsmount *m) |
| { |
| struct mount *mnt = real_mount(m); |
| br_write_lock(&vfsmount_lock); |
| if (mnt->mnt_pinned) { |
| mnt_add_count(mnt, 1); |
| mnt->mnt_pinned--; |
| } |
| br_write_unlock(&vfsmount_lock); |
| } |
| EXPORT_SYMBOL(mnt_unpin); |
| |
| static inline void mangle(struct seq_file *m, const char *s) |
| { |
| seq_escape(m, s, " \t\n\\"); |
| } |
| |
| /* |
| * Simple .show_options callback for filesystems which don't want to |
| * implement more complex mount option showing. |
| * |
| * See also save_mount_options(). |
| */ |
| int generic_show_options(struct seq_file *m, struct dentry *root) |
| { |
| const char *options; |
| |
| rcu_read_lock(); |
| options = rcu_dereference(root->d_sb->s_options); |
| |
| if (options != NULL && options[0]) { |
| seq_putc(m, ','); |
| mangle(m, options); |
| } |
| rcu_read_unlock(); |
| |
| return 0; |
| } |
| EXPORT_SYMBOL(generic_show_options); |
| |
| /* |
| * If filesystem uses generic_show_options(), this function should be |
| * called from the fill_super() callback. |
| * |
| * The .remount_fs callback usually needs to be handled in a special |
| * way, to make sure, that previous options are not overwritten if the |
| * remount fails. |
| * |
| * Also note, that if the filesystem's .remount_fs function doesn't |
| * reset all options to their default value, but changes only newly |
| * given options, then the displayed options will not reflect reality |
| * any more. |
| */ |
| void save_mount_options(struct super_block *sb, char *options) |
| { |
| BUG_ON(sb->s_options); |
| rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); |
| } |
| EXPORT_SYMBOL(save_mount_options); |
| |
| void replace_mount_options(struct super_block *sb, char *options) |
| { |
| char *old = sb->s_options; |
| rcu_assign_pointer(sb->s_options, options); |
| if (old) { |
| synchronize_rcu(); |
| kfree(old); |
| } |
| } |
| EXPORT_SYMBOL(replace_mount_options); |
| |
| #ifdef CONFIG_PROC_FS |
| /* iterator; we want it to have access to namespace_sem, thus here... */ |
| static void *m_start(struct seq_file *m, loff_t *pos) |
| { |
| struct proc_mounts *p = proc_mounts(m); |
| |
| down_read(&namespace_sem); |
| return seq_list_start(&p->ns->list, *pos); |
| } |
| |
| static void *m_next(struct seq_file *m, void *v, loff_t *pos) |
| { |
| struct proc_mounts *p = proc_mounts(m); |
| |
| return seq_list_next(v, &p->ns->list, pos); |
| } |
| |
| static void m_stop(struct seq_file *m, void *v) |
| { |
| up_read(&namespace_sem); |
| } |
| |
| static int m_show(struct seq_file *m, void *v) |
| { |
| struct proc_mounts *p = proc_mounts(m); |
| struct mount *r = list_entry(v, struct mount, mnt_list); |
| return p->show(m, &r->mnt); |
| } |
| |
| const struct seq_operations mounts_op = { |
| .start = m_start, |
| .next = m_next, |
| .stop = m_stop, |
| .show = m_show, |
| }; |
| #endif /* CONFIG_PROC_FS */ |
| |
| /** |
| * may_umount_tree - check if a mount tree is busy |
| * @mnt: root of mount tree |
| * |
| * This is called to check if a tree of mounts has any |
| * open files, pwds, chroots or sub mounts that are |
| * busy. |
| */ |
| int may_umount_tree(struct vfsmount *m) |
| { |
| struct mount *mnt = real_mount(m); |
| int actual_refs = 0; |
| int minimum_refs = 0; |
| struct mount *p; |
| BUG_ON(!m); |
| |
| /* write lock needed for mnt_get_count */ |
| br_write_lock(&vfsmount_lock); |
| for (p = mnt; p; p = next_mnt(p, mnt)) { |
| actual_refs += mnt_get_count(p); |
| minimum_refs += 2; |
| } |
| br_write_unlock(&vfsmount_lock); |
| |
| if (actual_refs > minimum_refs) |
| return 0; |
| |
| return 1; |
| } |
| |
| EXPORT_SYMBOL(may_umount_tree); |
| |
| /** |
| * may_umount - check if a mount point is busy |
| * @mnt: root of mount |
| * |
| * This is called to check if a mount point has any |
| * open files, pwds, chroots or sub mounts. If the |
| * mount has sub mounts this will return busy |
| * regardless of whether the sub mounts are busy. |
| * |
| * Doesn't take quota and stuff into account. IOW, in some cases it will |
| * give false negatives. The main reason why it's here is that we need |
| * a non-destructive way to look for easily umountable filesystems. |
| */ |
| int may_umount(struct vfsmount *mnt) |
| { |
| int ret = 1; |
| down_read(&namespace_sem); |
| br_write_lock(&vfsmount_lock); |
| if (propagate_mount_busy(real_mount(mnt), 2)) |
| ret = 0; |
| br_write_unlock(&vfsmount_lock); |
| up_read(&namespace_sem); |
| return ret; |
| } |
| |
| EXPORT_SYMBOL(may_umount); |
| |
| void release_mounts(struct list_head *head) |
| { |
| struct mount *mnt; |
| while (!list_empty(head)) { |
| mnt = list_first_entry(head, struct mount, mnt_hash); |
| list_del_init(&mnt->mnt_hash); |
| if (mnt_has_parent(mnt)) { |
| struct dentry *dentry; |
| struct mount *m; |
| |
| br_write_lock(&vfsmount_lock); |
| dentry = mnt->mnt_mountpoint; |
| m = mnt->mnt_parent; |
| mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
| mnt->mnt_parent = mnt; |
| m->mnt_ghosts--; |
| br_write_unlock(&vfsmount_lock); |
| dput(dentry); |
| mntput(&m->mnt); |
| } |
| mntput(&mnt->mnt); |
| } |
| } |
| |
| /* |
| * vfsmount lock must be held for write |
| * namespace_sem must be held for write |
| */ |
| void umount_tree(struct mount *mnt, int propagate, struct list_head *kill) |
| { |
| LIST_HEAD(tmp_list); |
| struct mount *p; |
| |
| for (p = mnt; p; p = next_mnt(p, mnt)) |
| list_move(&p->mnt_hash, &tmp_list); |
| |
| list_for_each_entry(p, &tmp_list, mnt_hash) |
| list_del_init(&p->mnt_child); |
| |
| if (propagate) |
| propagate_umount(&tmp_list); |
| |
| list_for_each_entry(p, &tmp_list, mnt_hash) { |
| list_del_init(&p->mnt_expire); |
| list_del_init(&p->mnt_list); |
| __touch_mnt_namespace(p->mnt_ns); |
| p->mnt_ns = NULL; |
| if (mnt_has_parent(p)) { |
| p->mnt_parent->mnt_ghosts++; |
| dentry_reset_mounted(p->mnt_mountpoint); |
| } |
| change_mnt_propagation(p, MS_PRIVATE); |
| } |
| list_splice(&tmp_list, kill); |
| } |
| |
| static void shrink_submounts(struct mount *mnt, struct list_head *umounts); |
| |
| static int do_umount(struct mount *mnt, int flags) |
| { |
| struct super_block *sb = mnt->mnt.mnt_sb; |
| int retval; |
| LIST_HEAD(umount_list); |
| |
| retval = security_sb_umount(&mnt->mnt, flags); |
| if (retval) |
| return retval; |
| |
| /* |
| * Allow userspace to request a mountpoint be expired rather than |
| * unmounting unconditionally. Unmount only happens if: |
| * (1) the mark is already set (the mark is cleared by mntput()) |
| * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] |
| */ |
| if (flags & MNT_EXPIRE) { |
| if (&mnt->mnt == current->fs->root.mnt || |
| flags & (MNT_FORCE | MNT_DETACH)) |
| return -EINVAL; |
| |
| /* |
| * probably don't strictly need the lock here if we examined |
| * all race cases, but it's a slowpath. |
| */ |
| br_write_lock(&vfsmount_lock); |
| if (mnt_get_count(mnt) != 2) { |
| br_write_unlock(&vfsmount_lock); |
| return -EBUSY; |
| } |
| br_write_unlock(&vfsmount_lock); |
| |
| if (!xchg(&mnt->mnt_expiry_mark, 1)) |
| return -EAGAIN; |
| } |
| |
| /* |
| * If we may have to abort operations to get out of this |
| * mount, and they will themselves hold resources we must |
| * allow the fs to do things. In the Unix tradition of |
| * 'Gee thats tricky lets do it in userspace' the umount_begin |
| * might fail to complete on the first run through as other tasks |
| * must return, and the like. Thats for the mount program to worry |
| * about for the moment. |
| */ |
| |
| if (flags & MNT_FORCE && sb->s_op->umount_begin) { |
| sb->s_op->umount_begin(sb); |
| } |
| |
| /* |
| * No sense to grab the lock for this test, but test itself looks |
| * somewhat bogus. Suggestions for better replacement? |
| * Ho-hum... In principle, we might treat that as umount + switch |
| * to rootfs. GC would eventually take care of the old vfsmount. |
| * Actually it makes sense, especially if rootfs would contain a |
| * /reboot - static binary that would close all descriptors and |
| * call reboot(9). Then init(8) could umount root and exec /reboot. |
| */ |
| if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { |
| /* |
| * Special case for "unmounting" root ... |
| * we just try to remount it readonly. |
| */ |
| down_write(&sb->s_umount); |
| if (!(sb->s_flags & MS_RDONLY)) |
| retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); |
| up_write(&sb->s_umount); |
| return retval; |
| } |
| |
| down_write(&namespace_sem); |
| br_write_lock(&vfsmount_lock); |
| event++; |
| |
| if (!(flags & MNT_DETACH)) |
| shrink_submounts(mnt, &umount_list); |
| |
| retval = -EBUSY; |
| if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { |
| if (!list_empty(&mnt->mnt_list)) |
| umount_tree(mnt, 1, &umount_list); |
| retval = 0; |
| } |
| br_write_unlock(&vfsmount_lock); |
| up_write(&namespace_sem); |
| release_mounts(&umount_list); |
| return retval; |
| } |
| |
| /* |
| * Now umount can handle mount points as well as block devices. |
| * This is important for filesystems which use unnamed block devices. |
| * |
| * We now support a flag for forced unmount like the other 'big iron' |
| * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD |
| */ |
| |
| SYSCALL_DEFINE2(umount, char __user *, name, int, flags) |
| { |
| struct path path; |
| struct mount *mnt; |
| int retval; |
| int lookup_flags = 0; |
| |
| if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) |
| return -EINVAL; |
| |
| if (!(flags & UMOUNT_NOFOLLOW)) |
| lookup_flags |= LOOKUP_FOLLOW; |
| |
| retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); |
| if (retval) |
| goto out; |
| mnt = real_mount(path.mnt); |
| retval = -EINVAL; |
| if (path.dentry != path.mnt->mnt_root) |
| goto dput_and_out; |
| if (!check_mnt(mnt)) |
| goto dput_and_out; |
| |
| retval = -EPERM; |
| if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) |
| goto dput_and_out; |
| |
| retval = do_umount(mnt, flags); |
| dput_and_out: |
| /* we mustn't call path_put() as that would clear mnt_expiry_mark */ |
| dput(path.dentry); |
| mntput_no_expire(mnt); |
| out: |
| return retval; |
| } |
| |
| #ifdef __ARCH_WANT_SYS_OLDUMOUNT |
| |
| /* |
| * The 2.0 compatible umount. No flags. |
| */ |
| SYSCALL_DEFINE1(oldumount, char __user *, name) |
| { |
| return sys_umount(name, 0); |
| } |
| |
| #endif |
| |
| static int mount_is_safe(struct path *path) |
| { |
| if (ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN)) |
| return 0; |
| return -EPERM; |
| #ifdef notyet |
| if (S_ISLNK(path->dentry->d_inode->i_mode)) |
| return -EPERM; |
| if (path->dentry->d_inode->i_mode & S_ISVTX) { |
| if (current_uid() != path->dentry->d_inode->i_uid) |
| return -EPERM; |
| } |
| if (inode_permission(path->dentry->d_inode, MAY_WRITE)) |
| return -EPERM; |
| return 0; |
| #endif |
| } |
| |
| static bool mnt_ns_loop(struct path *path) |
| { |
| /* Could bind mounting the mount namespace inode cause a |
| * mount namespace loop? |
| */ |
| struct inode *inode = path->dentry->d_inode; |
| struct proc_inode *ei; |
| struct mnt_namespace *mnt_ns; |
| |
| if (!proc_ns_inode(inode)) |
| return false; |
| |
| ei = PROC_I(inode); |
| if (ei->ns_ops != &mntns_operations) |
| return false; |
| |
| mnt_ns = ei->ns; |
| return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; |
| } |
| |
| struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, |
| int flag) |
| { |
| struct mount *res, *p, *q, *r; |
| struct path path; |
| |
| if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) |
| return ERR_PTR(-EINVAL); |
| |
| res = q = clone_mnt(mnt, dentry, flag); |
| if (IS_ERR(q)) |
| return q; |
| |
| q->mnt_mountpoint = mnt->mnt_mountpoint; |
| |
| p = mnt; |
| list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { |
| struct mount *s; |
| if (!is_subdir(r->mnt_mountpoint, dentry)) |
| continue; |
| |
| for (s = r; s; s = next_mnt(s, r)) { |
| if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { |
| s = skip_mnt_tree(s); |
| continue; |
| } |
| while (p != s->mnt_parent) { |
| p = p->mnt_parent; |
| q = q->mnt_parent; |
| } |
| p = s; |
| path.mnt = &q->mnt; |
| path.dentry = p->mnt_mountpoint; |
| q = clone_mnt(p, p->mnt.mnt_root, flag); |
| if (IS_ERR(q)) |
| goto out; |
| br_write_lock(&vfsmount_lock); |
| list_add_tail(&q->mnt_list, &res->mnt_list); |
| attach_mnt(q, &path); |
| br_write_unlock(&vfsmount_lock); |
| } |
| } |
| return res; |
| out: |
| if (res) { |
| LIST_HEAD(umount_list); |
| br_write_lock(&vfsmount_lock); |
| umount_tree(res, 0, &umount_list); |
| br_write_unlock(&vfsmount_lock); |
| release_mounts(&umount_list); |
| } |
| return q; |
| } |
| |
| /* Caller should check returned pointer for errors */ |
| |
| struct vfsmount *collect_mounts(struct path *path) |
| { |
| struct mount *tree; |
| down_write(&namespace_sem); |
| if (!check_mnt(real_mount(path->mnt))) |
| tree = ERR_PTR(-EINVAL); |
| else |
| tree = copy_tree(real_mount(path->mnt), path->dentry, |
| CL_COPY_ALL | CL_PRIVATE); |
| up_write(&namespace_sem); |
| if (IS_ERR(tree)) |
| return NULL; |
| return &tree->mnt; |
| } |
| |
| void drop_collected_mounts(struct vfsmount *mnt) |
| { |
| LIST_HEAD(umount_list); |
| down_write(&namespace_sem); |
| br_write_lock(&vfsmount_lock); |
| umount_tree(real_mount(mnt), 0, &umount_list); |
| br_write_unlock(&vfsmount_lock); |
| up_write(&namespace_sem); |
| release_mounts(&umount_list); |
| } |
| |
| int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, |
| struct vfsmount *root) |
| { |
| struct mount *mnt; |
| int res = f(root, arg); |
| if (res) |
| return res; |
| list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { |
| res = f(&mnt->mnt, arg); |
| if (res) |
| return res; |
| } |
| return 0; |
| } |
| |
| static void cleanup_group_ids(struct mount *mnt, struct mount *end) |
| { |
| struct mount *p; |
| |
| for (p = mnt; p != end; p = next_mnt(p, mnt)) { |
| if (p->mnt_group_id && !IS_MNT_SHARED(p)) |
| mnt_release_group_id(p); |
| } |
| } |
| |
| static int invent_group_ids(struct mount *mnt, bool recurse) |
| { |
| struct mount *p; |
| |
| for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { |
| if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { |
| int err = mnt_alloc_group_id(p); |
| if (err) { |
| cleanup_group_ids(mnt, p); |
| return err; |
| } |
| } |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * @source_mnt : mount tree to be attached |
| * @nd : place the mount tree @source_mnt is attached |
| * @parent_nd : if non-null, detach the source_mnt from its parent and |
| * store the parent mount and mountpoint dentry. |
| * (done when source_mnt is moved) |
| * |
| * NOTE: in the table below explains the semantics when a source mount |
| * of a given type is attached to a destination mount of a given type. |
| * --------------------------------------------------------------------------- |
| * | BIND MOUNT OPERATION | |
| * |************************************************************************** |
| * | source-->| shared | private | slave | unbindable | |
| * | dest | | | | | |
| * | | | | | | | |
| * | v | | | | | |
| * |************************************************************************** |
| * | shared | shared (++) | shared (+) | shared(+++)| invalid | |
| * | | | | | | |
| * |non-shared| shared (+) | private | slave (*) | invalid | |
| * *************************************************************************** |
| * A bind operation clones the source mount and mounts the clone on the |
| * destination mount. |
| * |
| * (++) the cloned mount is propagated to all the mounts in the propagation |
| * tree of the destination mount and the cloned mount is added to |
| * the peer group of the source mount. |
| * (+) the cloned mount is created under the destination mount and is marked |
| * as shared. The cloned mount is added to the peer group of the source |
| * mount. |
| * (+++) the mount is propagated to all the mounts in the propagation tree |
| * of the destination mount and the cloned mount is made slave |
| * of the same master as that of the source mount. The cloned mount |
| * is marked as 'shared and slave'. |
| * (*) the cloned mount is made a slave of the same master as that of the |
| * source mount. |
| * |
| * --------------------------------------------------------------------------- |
| * | MOVE MOUNT OPERATION | |
| * |************************************************************************** |
| * | source-->| shared | private | slave | unbindable | |
| * | dest | | | | | |
| * | | | | | | | |
| * | v | | | | | |
| * |************************************************************************** |
| * | shared | shared (+) | shared (+) | shared(+++) | invalid | |
| * | | | | | | |
| * |non-shared| shared (+*) | private | slave (*) | unbindable | |
| * *************************************************************************** |
| * |
| * (+) the mount is moved to the destination. And is then propagated to |
| * all the mounts in the propagation tree of the destination mount. |
| * (+*) the mount is moved to the destination. |
| * (+++) the mount is moved to the destination and is then propagated to |
| * all the mounts belonging to the destination mount's propagation tree. |
| * the mount is marked as 'shared and slave'. |
| * (*) the mount continues to be a slave at the new location. |
| * |
| * if the source mount is a tree, the operations explained above is |
| * applied to each mount in the tree. |
| * Must be called without spinlocks held, since this function can sleep |
| * in allocations. |
| */ |
| static int attach_recursive_mnt(struct mount *source_mnt, |
| struct path *path, struct path *parent_path) |
| { |
| LIST_HEAD(tree_list); |
| struct mount *dest_mnt = real_mount(path->mnt); |
| struct dentry *dest_dentry = path->dentry; |
| struct mount *child, *p; |
| int err; |
| |
| if (IS_MNT_SHARED(dest_mnt)) { |
| err = invent_group_ids(source_mnt, true); |
| if (err) |
| goto out; |
| } |
| err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list); |
| if (err) |
| goto out_cleanup_ids; |
| |
| br_write_lock(&vfsmount_lock); |
| |
| if (IS_MNT_SHARED(dest_mnt)) { |
| for (p = source_mnt; p; p = next_mnt(p, source_mnt)) |
| set_mnt_shared(p); |
| } |
| if (parent_path) { |
| detach_mnt(source_mnt, parent_path); |
| attach_mnt(source_mnt, path); |
| touch_mnt_namespace(source_mnt->mnt_ns); |
| } else { |
| mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); |
| commit_tree(source_mnt); |
| } |
| |
| list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { |
| list_del_init(&child->mnt_hash); |
| commit_tree(child); |
| } |
| br_write_unlock(&vfsmount_lock); |
| |
| return 0; |
| |
| out_cleanup_ids: |
| if (IS_MNT_SHARED(dest_mnt)) |
| cleanup_group_ids(source_mnt, NULL); |
| out: |
| return err; |
| } |
| |
| static int lock_mount(struct path *path) |
| { |
| struct vfsmount *mnt; |
| retry: |
| mutex_lock(&path->dentry->d_inode->i_mutex); |
| if (unlikely(cant_mount(path->dentry))) { |
| mutex_unlock(&path->dentry->d_inode->i_mutex); |
| return -ENOENT; |
| } |
| down_write(&namespace_sem); |
| mnt = lookup_mnt(path); |
| if (likely(!mnt)) |
| return 0; |
| up_write(&namespace_sem); |
| mutex_unlock(&path->dentry->d_inode->i_mutex); |
| path_put(path); |
| path->mnt = mnt; |
| path->dentry = dget(mnt->mnt_root); |
| goto retry; |
| } |
| |
| static void unlock_mount(struct path *path) |
| { |
| up_write(&namespace_sem); |
| mutex_unlock(&path->dentry->d_inode->i_mutex); |
| } |
| |
| static int graft_tree(struct mount *mnt, struct path *path) |
| { |
| if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER) |
| return -EINVAL; |
| |
| if (S_ISDIR(path->dentry->d_inode->i_mode) != |
| S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode)) |
| return -ENOTDIR; |
| |
| if (d_unlinked(path->dentry)) |
| return -ENOENT; |
| |
| return attach_recursive_mnt(mnt, path, NULL); |
| } |
| |
| /* |
| * Sanity check the flags to change_mnt_propagation. |
| */ |
| |
| static int flags_to_propagation_type(int flags) |
| { |
| int type = flags & ~(MS_REC | MS_SILENT); |
| |
| /* Fail if any non-propagation flags are set */ |
| if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
| return 0; |
| /* Only one propagation flag should be set */ |
| if (!is_power_of_2(type)) |
| return 0; |
| return type; |
| } |
| |
| /* |
| * recursively change the type of the mountpoint. |
| */ |
| static int do_change_type(struct path *path, int flag) |
| { |
| struct mount *m; |
| struct mount *mnt = real_mount(path->mnt); |
| int recurse = flag & MS_REC; |
| int type; |
| int err = 0; |
| |
| if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) |
| return -EPERM; |
| |
| if (path->dentry != path->mnt->mnt_root) |
| return -EINVAL; |
| |
| type = flags_to_propagation_type(flag); |
| if (!type) |
| return -EINVAL; |
| |
| down_write(&namespace_sem); |
| if (type == MS_SHARED) { |
| err = invent_group_ids(mnt, recurse); |
| if (err) |
| goto out_unlock; |
| } |
| |
| br_write_lock(&vfsmount_lock); |
| for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) |
| change_mnt_propagation(m, type); |
| br_write_unlock(&vfsmount_lock); |
| |
| out_unlock: |
| up_write(&namespace_sem); |
| return err; |
| } |
| |
| /* |
| * do loopback mount. |
| */ |
| static int do_loopback(struct path *path, const char *old_name, |
| int recurse) |
| { |
| LIST_HEAD(umount_list); |
| struct path old_path; |
| struct mount *mnt = NULL, *old; |
| int err = mount_is_safe(path); |
| if (err) |
| return err; |
| if (!old_name || !*old_name) |
| return -EINVAL; |
| err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); |
| if (err) |
| return err; |
| |
| err = -EINVAL; |
| if (mnt_ns_loop(&old_path)) |
| goto out; |
| |
| err = lock_mount(path); |
| if (err) |
| goto out; |
| |
| old = real_mount(old_path.mnt); |
| |
| err = -EINVAL; |
| if (IS_MNT_UNBINDABLE(old)) |
| goto out2; |
| |
| if (!check_mnt(real_mount(path->mnt)) || !check_mnt(old)) |
| goto out2; |
| |
| if (recurse) |
| mnt = copy_tree(old, old_path.dentry, 0); |
| else |
| mnt = clone_mnt(old, old_path.dentry, 0); |
| |
| if (IS_ERR(mnt)) { |
| err = PTR_ERR(mnt); |
| goto out; |
| } |
| |
| err = graft_tree(mnt, path); |
| if (err) { |
| br_write_lock(&vfsmount_lock); |
| umount_tree(mnt, 0, &umount_list); |
| br_write_unlock(&vfsmount_lock); |
| } |
| out2: |
| unlock_mount(path); |
| release_mounts(&umount_list); |
| out: |
| path_put(&old_path); |
| return err; |
| } |
| |
| static int change_mount_flags(struct vfsmount *mnt, int ms_flags) |
| { |
| int error = 0; |
| int readonly_request = 0; |
| |
| if (ms_flags & MS_RDONLY) |
| readonly_request = 1; |
| if (readonly_request == __mnt_is_readonly(mnt)) |
| return 0; |
| |
| if (readonly_request) |
| error = mnt_make_readonly(real_mount(mnt)); |
| else |
| __mnt_unmake_readonly(real_mount(mnt)); |
| return error; |
| } |
| |
| /* |
| * change filesystem flags. dir should be a physical root of filesystem. |
| * If you've mounted a non-root directory somewhere and want to do remount |
| * on it - tough luck. |
| */ |
| static int do_remount(struct path *path, int flags, int mnt_flags, |
| void *data) |
| { |
| int err; |
| struct super_block *sb = path->mnt->mnt_sb; |
| struct mount *mnt = real_mount(path->mnt); |
| |
| if (!capable(CAP_SYS_ADMIN)) |
| return -EPERM; |
| |
| if (!check_mnt(mnt)) |
| return -EINVAL; |
| |
| if (path->dentry != path->mnt->mnt_root) |
| return -EINVAL; |
| |
| err = security_sb_remount(sb, data); |
| if (err) |
| return err; |
| |
| down_write(&sb->s_umount); |
| if (flags & MS_BIND) |
| err = change_mount_flags(path->mnt, flags); |
| else { |
| err = do_remount_sb2(path->mnt, sb, flags, data, 0); |
| br_write_lock(&vfsmount_lock); |
| propagate_remount(mnt); |
| br_write_unlock(&vfsmount_lock); |
| } |
| if (!err) { |
| br_write_lock(&vfsmount_lock); |
| mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK; |
| mnt->mnt.mnt_flags = mnt_flags; |
| br_write_unlock(&vfsmount_lock); |
| } |
| up_write(&sb->s_umount); |
| if (!err) { |
| br_write_lock(&vfsmount_lock); |
| touch_mnt_namespace(mnt->mnt_ns); |
| br_write_unlock(&vfsmount_lock); |
| } |
| return err; |
| } |
| |
| static inline int tree_contains_unbindable(struct mount *mnt) |
| { |
| struct mount *p; |
| for (p = mnt; p; p = next_mnt(p, mnt)) { |
| if (IS_MNT_UNBINDABLE(p)) |
| return 1; |
| } |
| return 0; |
| } |
| |
| static int do_move_mount(struct path *path, const char *old_name) |
| { |
| struct path old_path, parent_path; |
| struct mount *p; |
| struct mount *old; |
| int err = 0; |
| if (!ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN)) |
| return -EPERM; |
| if (!old_name || !*old_name) |
| return -EINVAL; |
| err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
| if (err) |
| return err; |
| |
| err = lock_mount(path); |
| if (err < 0) |
| goto out; |
| |
| old = real_mount(old_path.mnt); |
| p = real_mount(path->mnt); |
| |
| err = -EINVAL; |
| if (!check_mnt(p) || !check_mnt(old)) |
| goto out1; |
| |
| if (d_unlinked(path->dentry)) |
| goto out1; |
| |
| err = -EINVAL; |
| if (old_path.dentry != old_path.mnt->mnt_root) |
| goto out1; |
| |
| if (!mnt_has_parent(old)) |
| goto out1; |
| |
| if (S_ISDIR(path->dentry->d_inode->i_mode) != |
| S_ISDIR(old_path.dentry->d_inode->i_mode)) |
| goto out1; |
| /* |
| * Don't move a mount residing in a shared parent. |
| */ |
| if (IS_MNT_SHARED(old->mnt_parent)) |
| goto out1; |
| /* |
| * Don't move a mount tree containing unbindable mounts to a destination |
| * mount which is shared. |
| */ |
| if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) |
| goto out1; |
| err = -ELOOP; |
| for (; mnt_has_parent(p); p = p->mnt_parent) |
| if (p == old) |
| goto out1; |
| |
| err = attach_recursive_mnt(old, path, &parent_path); |
| if (err) |
| goto out1; |
| |
| /* if the mount is moved, it should no longer be expire |
| * automatically */ |
| list_del_init(&old->mnt_expire); |
| out1: |
| unlock_mount(path); |
| out: |
| if (!err) |
| path_put(&parent_path); |
| path_put(&old_path); |
| return err; |
| } |
| |
| static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) |
| { |
| int err; |
| const char *subtype = strchr(fstype, '.'); |
| if (subtype) { |
| subtype++; |
| err = -EINVAL; |
| if (!subtype[0]) |
| goto err; |
| } else |
| subtype = ""; |
| |
| mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); |
| err = -ENOMEM; |
| if (!mnt->mnt_sb->s_subtype) |
| goto err; |
| return mnt; |
| |
| err: |
| mntput(mnt); |
| return ERR_PTR(err); |
| } |
| |
| /* |
| * add a mount into a namespace's mount tree |
| */ |
| static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) |
| { |
| int err; |
| |
| mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL); |
| |
| err = lock_mount(path); |
| if (err) |
| return err; |
| |
| err = -EINVAL; |
| if (unlikely(!check_mnt(real_mount(path->mnt)))) { |
| /* that's acceptable only for automounts done in private ns */ |
| if (!(mnt_flags & MNT_SHRINKABLE)) |
| goto unlock; |
| /* ... and for those we'd better have mountpoint still alive */ |
| if (!real_mount(path->mnt)->mnt_ns) |
| goto unlock; |
| } |
| |
| /* Refuse the same filesystem on the same mount point */ |
| err = -EBUSY; |
| if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && |
| path->mnt->mnt_root == path->dentry) |
| goto unlock; |
| |
| err = -EINVAL; |
| if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode)) |
| goto unlock; |
| |
| newmnt->mnt.mnt_flags = mnt_flags; |
| err = graft_tree(newmnt, path); |
| |
| unlock: |
| unlock_mount(path); |
| return err; |
| } |
| |
| /* |
| * create a new mount for userspace and request it to be added into the |
| * namespace's tree |
| */ |
| static int do_new_mount(struct path *path, const char *fstype, int flags, |
| int mnt_flags, const char *name, void *data) |
| { |
| struct file_system_type *type; |
| struct user_namespace *user_ns; |
| struct vfsmount *mnt; |
| int err; |
| |
| if (!fstype) |
| return -EINVAL; |
| |
| /* we need capabilities... */ |
| user_ns = real_mount(path->mnt)->mnt_ns->user_ns; |
| if (!ns_capable(user_ns, CAP_SYS_ADMIN)) |
| return -EPERM; |
| |
| type = get_fs_type(fstype); |
| if (!type) |
| return -ENODEV; |
| |
| if (user_ns != &init_user_ns) { |
| if (!(type->fs_flags & FS_USERNS_MOUNT)) { |
| put_filesystem(type); |
| return -EPERM; |
| } |
| /* Only in special cases allow devices from mounts |
| * created outside the initial user namespace. |
| */ |
| if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) { |
| flags |= MS_NODEV; |
| mnt_flags |= MNT_NODEV; |
| } |
| } |
| |
| mnt = vfs_kern_mount(type, flags, name, data); |
| if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && |
| !mnt->mnt_sb->s_subtype) |
| mnt = fs_set_subtype(mnt, fstype); |
| |
| put_filesystem(type); |
| if (IS_ERR(mnt)) |
| return PTR_ERR(mnt); |
| |
| err = do_add_mount(real_mount(mnt), path, mnt_flags); |
| if (err) |
| mntput(mnt); |
| return err; |
| } |
| |
| int finish_automount(struct vfsmount *m, struct path *path) |
| { |
| struct mount *mnt = real_mount(m); |
| int err; |
| /* The new mount record should have at least 2 refs to prevent it being |
| * expired before we get a chance to add it |
| */ |
| BUG_ON(mnt_get_count(mnt) < 2); |
| |
| if (m->mnt_sb == path->mnt->mnt_sb && |
| m->mnt_root == path->dentry) { |
| err = -ELOOP; |
| goto fail; |
| } |
| |
| err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); |
| if (!err) |
| return 0; |
| fail: |
| /* remove m from any expiration list it may be on */ |
| if (!list_empty(&mnt->mnt_expire)) { |
| down_write(&namespace_sem); |
| br_write_lock(&vfsmount_lock); |
| list_del_init(&mnt->mnt_expire); |
| br_write_unlock(&vfsmount_lock); |
| up_write(&namespace_sem); |
| } |
| mntput(m); |
| mntput(m); |
| return err; |
| } |
| |
| /** |
| * mnt_set_expiry - Put a mount on an expiration list |
| * @mnt: The mount to list. |
| * @expiry_list: The list to add the mount to. |
| */ |
| void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) |
| { |
| down_write(&namespace_sem); |
| br_write_lock(&vfsmount_lock); |
| |
| list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); |
| |
| br_write_unlock(&vfsmount_lock); |
| up_write(&namespace_sem); |
| } |
| EXPORT_SYMBOL(mnt_set_expiry); |
| |
| /* |
| * process a list of expirable mountpoints with the intent of discarding any |
| * mountpoints that aren't in use and haven't been touched since last we came |
| * here |
| */ |
| void mark_mounts_for_expiry(struct list_head *mounts) |
| { |
| struct mount *mnt, *next; |
| LIST_HEAD(graveyard); |
| LIST_HEAD(umounts); |
| |
| if (list_empty(mounts)) |
| return; |
| |
| down_write(&namespace_sem); |
| br_write_lock(&vfsmount_lock); |
| |
| /* extract from the expiration list every vfsmount that matches the |
| * following criteria: |
| * - only referenced by its parent vfsmount |
| * - still marked for expiry (marked on the last call here; marks are |
| * cleared by mntput()) |
| */ |
| list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { |
| if (!xchg(&mnt->mnt_expiry_mark, 1) || |
| propagate_mount_busy(mnt, 1)) |
| continue; |
| list_move(&mnt->mnt_expire, &graveyard); |
| } |
| while (!list_empty(&graveyard)) { |
| mnt = list_first_entry(&graveyard, struct mount, mnt_expire); |
| touch_mnt_namespace(mnt->mnt_ns); |
| umount_tree(mnt, 1, &umounts); |
| } |
| br_write_unlock(&vfsmount_lock); |
| up_write(&namespace_sem); |
| |
| release_mounts(&umounts); |
| } |
| |
| EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); |
| |
| /* |
| * Ripoff of 'select_parent()' |
| * |
| * search the list of submounts for a given mountpoint, and move any |
| * shrinkable submounts to the 'graveyard' list. |
| */ |
| static int select_submounts(struct mount *parent, struct list_head *graveyard) |
| { |
| struct mount *this_parent = parent; |
| struct list_head *next; |
| int found = 0; |
| |
| repeat: |
| next = this_parent->mnt_mounts.next; |
| resume: |
| while (next != &this_parent->mnt_mounts) { |
| struct list_head *tmp = next; |
| struct mount *mnt = list_entry(tmp, struct mount, mnt_child); |
| |
| next = tmp->next; |
| if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) |
| continue; |
| /* |
| * Descend a level if the d_mounts list is non-empty. |
| */ |
| if (!list_empty(&mnt->mnt_mounts)) { |
| this_parent = mnt; |
| goto repeat; |
| } |
| |
| if (!propagate_mount_busy(mnt, 1)) { |
| list_move_tail(&mnt->mnt_expire, graveyard); |
| found++; |
| } |
| } |
| /* |
| * All done at this level ... ascend and resume the search |
| */ |
| if (this_parent != parent) { |
| next = this_parent->mnt_child.next; |
| this_parent = this_parent->mnt_parent; |
| goto resume; |
| } |
| return found; |
| } |
| |
| /* |
| * process a list of expirable mountpoints with the intent of discarding any |
| * submounts of a specific parent mountpoint |
| * |
| * vfsmount_lock must be held for write |
| */ |
| static void shrink_submounts(struct mount *mnt, struct list_head *umounts) |
| { |
| LIST_HEAD(graveyard); |
| struct mount *m; |
| |
| /* extract submounts of 'mountpoint' from the expiration list */ |
| while (select_submounts(mnt, &graveyard)) { |
| while (!list_empty(&graveyard)) { |
| m = list_first_entry(&graveyard, struct mount, |
| mnt_expire); |
| touch_mnt_namespace(m->mnt_ns); |
| umount_tree(m, 1, umounts); |
| } |
| } |
| } |
| |
| /* |
| * Some copy_from_user() implementations do not return the exact number of |
| * bytes remaining to copy on a fault. But copy_mount_options() requires that. |
| * Note that this function differs from copy_from_user() in that it will oops |
| * on bad values of `to', rather than returning a short copy. |
| */ |
| static long exact_copy_from_user(void *to, const void __user * from, |
| unsigned long n) |
| { |
| char *t = to; |
| const char __user *f = from; |
| char c; |
| |
| if (!access_ok(VERIFY_READ, from, n)) |
| return n; |
| |
| while (n) { |
| if (__get_user(c, f)) { |
| memset(t, 0, n); |
| break; |
| } |
| *t++ = c; |
| f++; |
| n--; |
| } |
| return n; |
| } |
| |
| int copy_mount_options(const void __user * data, unsigned long *where) |
| { |
| int i; |
| unsigned long page; |
| unsigned long size; |
| |
| *where = 0; |
| if (!data) |
| return 0; |
| |
| if (!(page = __get_free_page(GFP_KERNEL))) |
| return -ENOMEM; |
| |
| /* We only care that *some* data at the address the user |
| * gave us is valid. Just in case, we'll zero |
| * the remainder of the page. |
| */ |
| /* copy_from_user cannot cross TASK_SIZE ! */ |
| size = TASK_SIZE - (unsigned long)data; |
| if (size > PAGE_SIZE) |
| size = PAGE_SIZE; |
| |
| i = size - exact_copy_from_user((void *)page, data, size); |
| if (!i) { |
| free_page(page); |
| return -EFAULT; |
| } |
| if (i != PAGE_SIZE) |
| memset((char *)page + i, 0, PAGE_SIZE - i); |
| *where = page; |
| return 0; |
| } |
| |
| int copy_mount_string(const void __user *data, char **where) |
| { |
| char *tmp; |
| |
| if (!data) { |
| *where = NULL; |
| return 0; |
| } |
| |
| tmp = strndup_user(data, PAGE_SIZE); |
| if (IS_ERR(tmp)) |
| return PTR_ERR(tmp); |
| |
| *where = tmp; |
| return 0; |
| } |
| |
| /* |
| * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to |
| * be given to the mount() call (ie: read-only, no-dev, no-suid etc). |
| * |
| * data is a (void *) that can point to any structure up to |
| * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent |
| * information (or be NULL). |
| * |
| * Pre-0.97 versions of mount() didn't have a flags word. |
| * When the flags word was introduced its top half was required |
| * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. |
| * Therefore, if this magic number is present, it carries no information |
| * and must be discarded. |
| */ |
| long do_mount(const char *dev_name, const char *dir_name, |
| const char *type_page, unsigned long flags, void *data_page) |
| { |
| struct path path; |
| int retval = 0; |
| int mnt_flags = 0; |
| |
| /* Discard magic */ |
| if ((flags & MS_MGC_MSK) == MS_MGC_VAL) |
| flags &= ~MS_MGC_MSK; |
| |
| /* Basic sanity checks */ |
| |
| if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) |
| return -EINVAL; |
| |
| if (data_page) |
| ((char *)data_page)[PAGE_SIZE - 1] = 0; |
| |
| /* ... and get the mountpoint */ |
| retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); |
| if (retval) |
| return retval; |
| |
| retval = security_sb_mount(dev_name, &path, |
| type_page, flags, data_page); |
| if (retval) |
| goto dput_out; |
| |
| /* Default to relatime unless overriden */ |
| if (!(flags & MS_NOATIME)) |
| mnt_flags |= MNT_RELATIME; |
| |
| /* Separate the per-mountpoint flags */ |
| if (flags & MS_NOSUID) |
| mnt_flags |= MNT_NOSUID; |
| if (flags & MS_NODEV) |
| mnt_flags |= MNT_NODEV; |
| if (flags & MS_NOEXEC) |
| mnt_flags |= MNT_NOEXEC; |
| if (flags & MS_NOATIME) |
| mnt_flags |= MNT_NOATIME; |
| if (flags & MS_NODIRATIME) |
| mnt_flags |= MNT_NODIRATIME; |
| if (flags & MS_STRICTATIME) |
| mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); |
| if (flags & MS_RDONLY) |
| mnt_flags |= MNT_READONLY; |
| |
| flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | |
| MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | |
| MS_STRICTATIME); |
| |
| if (flags & MS_REMOUNT) |
| retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, |
| data_page); |
| else if (flags & MS_BIND) |
| retval = do_loopback(&path, dev_name, flags & MS_REC); |
| else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
| retval = do_change_type(&path, flags); |
| else if (flags & MS_MOVE) |
| retval = do_move_mount(&path, dev_name); |
| else |
| retval = do_new_mount(&path, type_page, flags, mnt_flags, |
| dev_name, data_page); |
| dput_out: |
| path_put(&path); |
| return retval; |
| } |
| |
| |
| static void free_mnt_ns(struct mnt_namespace *ns) |
| { |
| proc_free_inum(ns->proc_inum); |
| put_user_ns(ns->user_ns); |
| kfree(ns); |
| } |
| |
| /* |
| * Assign a sequence number so we can detect when we attempt to bind |
| * mount a reference to an older mount namespace into the current |
| * mount namespace, preventing reference counting loops. A 64bit |
| * number incrementing at 10Ghz will take 12,427 years to wrap which |
| * is effectively never, so we can ignore the possibility. |
| */ |
| static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); |
| |
| static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns) |
| { |
| struct mnt_namespace *new_ns; |
| int ret; |
| |
| new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); |
| if (!new_ns) |
| return ERR_PTR(-ENOMEM); |
| ret = proc_alloc_inum(&new_ns->proc_inum); |
| if (ret) { |
| kfree(new_ns); |
| return ERR_PTR(ret); |
| } |
| new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); |
| atomic_set(&new_ns->count, 1); |
| new_ns->root = NULL; |
| INIT_LIST_HEAD(&new_ns->list); |
| init_waitqueue_head(&new_ns->poll); |
| new_ns->event = 0; |
| new_ns->user_ns = get_user_ns(user_ns); |
| return new_ns; |
| } |
| |
| /* |
| * Allocate a new namespace structure and populate it with contents |
| * copied from the namespace of the passed in task structure. |
| */ |
| static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, |
| struct user_namespace *user_ns, struct fs_struct *fs) |
| { |
| struct mnt_namespace *new_ns; |
| struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; |
| struct mount *p, *q; |
| struct mount *old = mnt_ns->root; |
| struct mount *new; |
| int copy_flags; |
| |
| new_ns = alloc_mnt_ns(user_ns); |
| if (IS_ERR(new_ns)) |
| return new_ns; |
| |
| down_write(&namespace_sem); |
| /* First pass: copy the tree topology */ |
| copy_flags = CL_COPY_ALL | CL_EXPIRE; |
| if (user_ns != mnt_ns->user_ns) |
| copy_flags |= CL_SHARED_TO_SLAVE; |
| new = copy_tree(old, old->mnt.mnt_root, copy_flags); |
| if (IS_ERR(new)) { |
| up_write(&namespace_sem); |
| free_mnt_ns(new_ns); |
| return ERR_CAST(new); |
| } |
| new_ns->root = new; |
| br_write_lock(&vfsmount_lock); |
| list_add_tail(&new_ns->list, &new->mnt_list); |
| br_write_unlock(&vfsmount_lock); |
| |
| /* |
| * Second pass: switch the tsk->fs->* elements and mark new vfsmounts |
| * as belonging to new namespace. We have already acquired a private |
| * fs_struct, so tsk->fs->lock is not needed. |
| */ |
| p = old; |
| q = new; |
| while (p) { |
| q->mnt_ns = new_ns; |
| if (fs) { |
| if (&p->mnt == fs->root.mnt) { |
| fs->root.mnt = mntget(&q->mnt); |
| rootmnt = &p->mnt; |
| } |
| if (&p->mnt == fs->pwd.mnt) { |
| fs->pwd.mnt = mntget(&q->mnt); |
| pwdmnt = &p->mnt; |
| } |
| } |
| p = next_mnt(p, old); |
| q = next_mnt(q, new); |
| } |
| up_write(&namespace_sem); |
| |
| if (rootmnt) |
| mntput(rootmnt); |
| if (pwdmnt) |
| mntput(pwdmnt); |
| |
| return new_ns; |
| } |
| |
| struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, |
| struct user_namespace *user_ns, struct fs_struct *new_fs) |
| { |
| struct mnt_namespace *new_ns; |
| |
| BUG_ON(!ns); |
| get_mnt_ns(ns); |
| |
| if (!(flags & CLONE_NEWNS)) |
| return ns; |
| |
| new_ns = dup_mnt_ns(ns, user_ns, new_fs); |
| |
| put_mnt_ns(ns); |
| return new_ns; |
| } |
| |
| /** |
| * create_mnt_ns - creates a private namespace and adds a root filesystem |
| * @mnt: pointer to the new root filesystem mountpoint |
| */ |
| static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) |
| { |
| struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns); |
| if (!IS_ERR(new_ns)) { |
| struct mount *mnt = real_mount(m); |
| mnt->mnt_ns = new_ns; |
| new_ns->root = mnt; |
| list_add(&new_ns->list, &mnt->mnt_list); |
| } else { |
| mntput(m); |
| } |
| return new_ns; |
| } |
| |
| struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) |
| { |
| struct mnt_namespace *ns; |
| struct super_block *s; |
| struct path path; |
| int err; |
| |
| ns = create_mnt_ns(mnt); |
| if (IS_ERR(ns)) |
| return ERR_CAST(ns); |
| |
| err = vfs_path_lookup(mnt->mnt_root, mnt, |
| name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); |
| |
| put_mnt_ns(ns); |
| |
| if (err) |
| return ERR_PTR(err); |
| |
| /* trade a vfsmount reference for active sb one */ |
| s = path.mnt->mnt_sb; |
| atomic_inc(&s->s_active); |
| mntput(path.mnt); |
| /* lock the sucker */ |
| down_write(&s->s_umount); |
| /* ... and return the root of (sub)tree on it */ |
| return path.dentry; |
| } |
| EXPORT_SYMBOL(mount_subtree); |
| |
| SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, |
| char __user *, type, unsigned long, flags, void __user *, data) |
| { |
| int ret; |
| char *kernel_type; |
| char *kernel_dir; |
| char *kernel_dev; |
| unsigned long data_page; |
| |
| ret = copy_mount_string(type, &kernel_type); |
| if (ret < 0) |
| goto out_type; |
| |
| kernel_dir = getname(dir_name); |
| if (IS_ERR(kernel_dir)) { |
| ret = PTR_ERR(kernel_dir); |
| goto out_dir; |
| } |
| |
| ret = copy_mount_string(dev_name, &kernel_dev); |
| if (ret < 0) |
| goto out_dev; |
| |
| ret = copy_mount_options(data, &data_page); |
| if (ret < 0) |
| goto out_data; |
| |
| ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags, |
| (void *) data_page); |
| |
| free_page(data_page); |
| out_data: |
| kfree(kernel_dev); |
| out_dev: |
| putname(kernel_dir); |
| out_dir: |
| kfree(kernel_type); |
| out_type: |
| return ret; |
| } |
| |
| /* |
| * Return true if path is reachable from root |
| * |
| * namespace_sem or vfsmount_lock is held |
| */ |
| bool is_path_reachable(struct mount *mnt, struct dentry *dentry, |
| const struct path *root) |
| { |
| while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { |
| dentry = mnt->mnt_mountpoint; |
| mnt = mnt->mnt_parent; |
| } |
| return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); |
| } |
| |
| int path_is_under(struct path *path1, struct path *path2) |
| { |
| int res; |
| br_read_lock(&vfsmount_lock); |
| res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); |
| br_read_unlock(&vfsmount_lock); |
| return res; |
| } |
| EXPORT_SYMBOL(path_is_under); |
| |
| /* |
| * pivot_root Semantics: |
| * Moves the root file system of the current process to the directory put_old, |
| * makes new_root as the new root file system of the current process, and sets |
| * root/cwd of all processes which had them on the current root to new_root. |
| * |
| * Restrictions: |
| * The new_root and put_old must be directories, and must not be on the |
| * same file system as the current process root. The put_old must be |
| * underneath new_root, i.e. adding a non-zero number of /.. to the string |
| * pointed to by put_old must yield the same directory as new_root. No other |
| * file system may be mounted on put_old. After all, new_root is a mountpoint. |
| * |
| * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. |
| * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives |
| * in this situation. |
| * |
| * Notes: |
| * - we don't move root/cwd if they are not at the root (reason: if something |
| * cared enough to change them, it's probably wrong to force them elsewhere) |
| * - it's okay to pick a root that isn't the root of a file system, e.g. |
| * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, |
| * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root |
| * first. |
| */ |
| SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, |
| const char __user *, put_old) |
| { |
| struct path new, old, parent_path, root_parent, root; |
| struct mount *new_mnt, *root_mnt; |
| int error; |
| |
| if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN)) |
| return -EPERM; |
| |
| error = user_path_dir(new_root, &new); |
| if (error) |
| goto out0; |
| |
| error = user_path_dir(put_old, &old); |
| if (error) |
| goto out1; |
| |
| error = security_sb_pivotroot(&old, &new); |
| if (error) |
| goto out2; |
| |
| get_fs_root(current->fs, &root); |
| error = lock_mount(&old); |
| if (error) |
| goto out3; |
| |
| error = -EINVAL; |
| new_mnt = real_mount(new.mnt); |
| root_mnt = real_mount(root.mnt); |
| if (IS_MNT_SHARED(real_mount(old.mnt)) || |
| IS_MNT_SHARED(new_mnt->mnt_parent) || |
| IS_MNT_SHARED(root_mnt->mnt_parent)) |
| goto out4; |
| if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) |
| goto out4; |
| error = -ENOENT; |
| if (d_unlinked(new.dentry)) |
| goto out4; |
| if (d_unlinked(old.dentry)) |
| goto out4; |
| error = -EBUSY; |
| if (new.mnt == root.mnt || |
| old.mnt == root.mnt) |
| goto out4; /* loop, on the same file system */ |
| error = -EINVAL; |
| if (root.mnt->mnt_root != root.dentry) |
| goto out4; /* not a mountpoint */ |
| if (!mnt_has_parent(root_mnt)) |
| goto out4; /* not attached */ |
| if (new.mnt->mnt_root != new.dentry) |
| goto out4; /* not a mountpoint */ |
| if (!mnt_has_parent(new_mnt)) |
| goto out4; /* not attached */ |
| /* make sure we can reach put_old from new_root */ |
| if (!is_path_reachable(real_mount(old.mnt), old.dentry, &new)) |
| goto out4; |
| /* make certain new is below the root */ |
| if (!is_path_reachable(new_mnt, new.dentry, &root)) |
| goto out4; |
| br_write_lock(&vfsmount_lock); |
| detach_mnt(new_mnt, &parent_path); |
| detach_mnt(root_mnt, &root_parent); |
| /* mount old root on put_old */ |
| attach_mnt(root_mnt, &old); |
| /* mount new_root on / */ |
| attach_mnt(new_mnt, &root_parent); |
| touch_mnt_namespace(current->nsproxy->mnt_ns); |
| br_write_unlock(&vfsmount_lock); |
| chroot_fs_refs(&root, &new); |
| error = 0; |
| out4: |
| unlock_mount(&old); |
| if (!error) { |
| path_put(&root_parent); |
| path_put(&parent_path); |
| } |
| out3: |
| path_put(&root); |
| out2: |
| path_put(&old); |
| out1: |
| path_put(&new); |
| out0: |
| return error; |
| } |
| |
| static void __init init_mount_tree(void) |
| { |
| struct vfsmount *mnt; |
| struct mnt_namespace *ns; |
| struct path root; |
| struct file_system_type *type; |
| |
| type = get_fs_type("rootfs"); |
| if (!type) |
| panic("Can't find rootfs type"); |
| mnt = vfs_kern_mount(type, 0, "rootfs", NULL); |
| put_filesystem(type); |
| if (IS_ERR(mnt)) |
| panic("Can't create rootfs"); |
| |
| ns = create_mnt_ns(mnt); |
| if (IS_ERR(ns)) |
| panic("Can't allocate initial namespace"); |
| |
| init_task.nsproxy->mnt_ns = ns; |
| get_mnt_ns(ns); |
| |
| root.mnt = mnt; |
| root.dentry = mnt->mnt_root; |
| |
| set_fs_pwd(current->fs, &root); |
| set_fs_root(current->fs, &root); |
| } |
| |
| void __init mnt_init(void) |
| { |
| unsigned u; |
| int err; |
| |
| init_rwsem(&namespace_sem); |
| |
| mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), |
| 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
| |
| mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); |
| |
| if (!mount_hashtable) |
| panic("Failed to allocate mount hash table\n"); |
| |
| printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE); |
| |
| for (u = 0; u < HASH_SIZE; u++) |
| INIT_LIST_HEAD(&mount_hashtable[u]); |
| |
| br_lock_init(&vfsmount_lock); |
| |
| err = sysfs_init(); |
| if (err) |
| printk(KERN_WARNING "%s: sysfs_init error: %d\n", |
| __func__, err); |
| fs_kobj = kobject_create_and_add("fs", NULL); |
| if (!fs_kobj) |
| printk(KERN_WARNING "%s: kobj create error\n", __func__); |
| init_rootfs(); |
| init_mount_tree(); |
| } |
| |
| void put_mnt_ns(struct mnt_namespace *ns) |
| { |
| LIST_HEAD(umount_list); |
| |
| if (!atomic_dec_and_test(&ns->count)) |
| return; |
| down_write(&namespace_sem); |
| br_write_lock(&vfsmount_lock); |
| umount_tree(ns->root, 0, &umount_list); |
| br_write_unlock(&vfsmount_lock); |
| up_write(&namespace_sem); |
| release_mounts(&umount_list); |
| free_mnt_ns(ns); |
| } |
| |
| struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) |
| { |
| struct vfsmount *mnt; |
| mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); |
| if (!IS_ERR(mnt)) { |
| /* |
| * it is a longterm mount, don't release mnt until |
| * we unmount before file sys is unregistered |
| */ |
| real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; |
| } |
| return mnt; |
| } |
| EXPORT_SYMBOL_GPL(kern_mount_data); |
| |
| void kern_unmount(struct vfsmount *mnt) |
| { |
| /* release long term mount so mount point can be released */ |
| if (!IS_ERR_OR_NULL(mnt)) { |
| br_write_lock(&vfsmount_lock); |
| real_mount(mnt)->mnt_ns = NULL; |
| br_write_unlock(&vfsmount_lock); |
| mntput(mnt); |
| } |
| } |
| EXPORT_SYMBOL(kern_unmount); |
| |
| bool our_mnt(struct vfsmount *mnt) |
| { |
| return check_mnt(real_mount(mnt)); |
| } |
| |
| static void *mntns_get(struct task_struct *task) |
| { |
| struct mnt_namespace *ns = NULL; |
| struct nsproxy *nsproxy; |
| |
| rcu_read_lock(); |
| nsproxy = task_nsproxy(task); |
| if (nsproxy) { |
| ns = nsproxy->mnt_ns; |
| get_mnt_ns(ns); |
| } |
| rcu_read_unlock(); |
| |
| return ns; |
| } |
| |
| static void mntns_put(void *ns) |
| { |
| put_mnt_ns(ns); |
| } |
| |
| static int mntns_install(struct nsproxy *nsproxy, void *ns) |
| { |
| struct fs_struct *fs = current->fs; |
| struct mnt_namespace *mnt_ns = ns; |
| struct path root; |
| |
| if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || |
| !nsown_capable(CAP_SYS_CHROOT)) |
| return -EINVAL; |
| |
| if (fs->users != 1) |
| return -EINVAL; |
| |
| get_mnt_ns(mnt_ns); |
| put_mnt_ns(nsproxy->mnt_ns); |
| nsproxy->mnt_ns = mnt_ns; |
| |
| /* Find the root */ |
| root.mnt = &mnt_ns->root->mnt; |
| root.dentry = mnt_ns->root->mnt.mnt_root; |
| path_get(&root); |
| while(d_mountpoint(root.dentry) && follow_down_one(&root)) |
| ; |
| |
| /* Update the pwd and root */ |
| set_fs_pwd(fs, &root); |
| set_fs_root(fs, &root); |
| |
| path_put(&root); |
| return 0; |
| } |
| |
| static unsigned int mntns_inum(void *ns) |
| { |
| struct mnt_namespace *mnt_ns = ns; |
| return mnt_ns->proc_inum; |
| } |
| |
| const struct proc_ns_operations mntns_operations = { |
| .name = "mnt", |
| .type = CLONE_NEWNS, |
| .get = mntns_get, |
| .put = mntns_put, |
| .install = mntns_install, |
| .inum = mntns_inum, |
| }; |