| /* |
| * |
| * Copyright (C) 2011 Novell Inc. |
| * |
| * This program is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 as published by |
| * the Free Software Foundation. |
| */ |
| |
| #include <linux/fs.h> |
| #include <linux/namei.h> |
| #include <linux/xattr.h> |
| #include <linux/security.h> |
| #include <linux/mount.h> |
| #include <linux/slab.h> |
| #include <linux/parser.h> |
| #include <linux/module.h> |
| #include <linux/sched.h> |
| #include <linux/statfs.h> |
| #include <linux/seq_file.h> |
| #include "overlayfs.h" |
| |
| MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>"); |
| MODULE_DESCRIPTION("Overlay filesystem"); |
| MODULE_LICENSE("GPL"); |
| |
| #define OVERLAYFS_SUPER_MAGIC 0x794c7630 |
| |
| struct ovl_config { |
| char *lowerdir; |
| char *upperdir; |
| char *workdir; |
| }; |
| |
| /* private information held for overlayfs's superblock */ |
| struct ovl_fs { |
| struct vfsmount *upper_mnt; |
| unsigned numlower; |
| struct vfsmount **lower_mnt; |
| struct dentry *workdir; |
| long lower_namelen; |
| /* pathnames of lower and upper dirs, for show_options */ |
| struct ovl_config config; |
| }; |
| |
| struct ovl_dir_cache; |
| |
| /* private information held for every overlayfs dentry */ |
| struct ovl_entry { |
| struct dentry *__upperdentry; |
| struct ovl_dir_cache *cache; |
| union { |
| struct { |
| u64 version; |
| bool opaque; |
| }; |
| struct rcu_head rcu; |
| }; |
| unsigned numlower; |
| struct path lowerstack[]; |
| }; |
| |
| #define OVL_MAX_STACK 500 |
| |
| static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe) |
| { |
| return oe->numlower ? oe->lowerstack[0].dentry : NULL; |
| } |
| |
| enum ovl_path_type ovl_path_type(struct dentry *dentry) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| enum ovl_path_type type = 0; |
| |
| if (oe->__upperdentry) { |
| type = __OVL_PATH_UPPER; |
| |
| if (oe->numlower) { |
| if (S_ISDIR(dentry->d_inode->i_mode)) |
| type |= __OVL_PATH_MERGE; |
| } else if (!oe->opaque) { |
| type |= __OVL_PATH_PURE; |
| } |
| } else { |
| if (oe->numlower > 1) |
| type |= __OVL_PATH_MERGE; |
| } |
| return type; |
| } |
| |
| static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe) |
| { |
| return lockless_dereference(oe->__upperdentry); |
| } |
| |
| void ovl_path_upper(struct dentry *dentry, struct path *path) |
| { |
| struct ovl_fs *ofs = dentry->d_sb->s_fs_info; |
| struct ovl_entry *oe = dentry->d_fsdata; |
| |
| path->mnt = ofs->upper_mnt; |
| path->dentry = ovl_upperdentry_dereference(oe); |
| } |
| |
| enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path) |
| { |
| enum ovl_path_type type = ovl_path_type(dentry); |
| |
| if (!OVL_TYPE_UPPER(type)) |
| ovl_path_lower(dentry, path); |
| else |
| ovl_path_upper(dentry, path); |
| |
| return type; |
| } |
| |
| struct dentry *ovl_dentry_upper(struct dentry *dentry) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| |
| return ovl_upperdentry_dereference(oe); |
| } |
| |
| struct dentry *ovl_dentry_lower(struct dentry *dentry) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| |
| return __ovl_dentry_lower(oe); |
| } |
| |
| struct dentry *ovl_dentry_real(struct dentry *dentry) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| struct dentry *realdentry; |
| |
| realdentry = ovl_upperdentry_dereference(oe); |
| if (!realdentry) |
| realdentry = __ovl_dentry_lower(oe); |
| |
| return realdentry; |
| } |
| |
| struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper) |
| { |
| struct dentry *realdentry; |
| |
| realdentry = ovl_upperdentry_dereference(oe); |
| if (realdentry) { |
| *is_upper = true; |
| } else { |
| realdentry = __ovl_dentry_lower(oe); |
| *is_upper = false; |
| } |
| return realdentry; |
| } |
| |
| struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| |
| return oe->cache; |
| } |
| |
| void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| |
| oe->cache = cache; |
| } |
| |
| void ovl_path_lower(struct dentry *dentry, struct path *path) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| |
| *path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL }; |
| } |
| |
| int ovl_want_write(struct dentry *dentry) |
| { |
| struct ovl_fs *ofs = dentry->d_sb->s_fs_info; |
| return mnt_want_write(ofs->upper_mnt); |
| } |
| |
| void ovl_drop_write(struct dentry *dentry) |
| { |
| struct ovl_fs *ofs = dentry->d_sb->s_fs_info; |
| mnt_drop_write(ofs->upper_mnt); |
| } |
| |
| struct dentry *ovl_workdir(struct dentry *dentry) |
| { |
| struct ovl_fs *ofs = dentry->d_sb->s_fs_info; |
| return ofs->workdir; |
| } |
| |
| bool ovl_dentry_is_opaque(struct dentry *dentry) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| return oe->opaque; |
| } |
| |
| void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| oe->opaque = opaque; |
| } |
| |
| void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| |
| WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex)); |
| WARN_ON(oe->__upperdentry); |
| BUG_ON(!upperdentry->d_inode); |
| /* |
| * Make sure upperdentry is consistent before making it visible to |
| * ovl_upperdentry_dereference(). |
| */ |
| smp_wmb(); |
| oe->__upperdentry = upperdentry; |
| } |
| |
| void ovl_dentry_version_inc(struct dentry *dentry) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| |
| WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex)); |
| oe->version++; |
| } |
| |
| u64 ovl_dentry_version_get(struct dentry *dentry) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| |
| WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex)); |
| return oe->version; |
| } |
| |
| bool ovl_is_whiteout(struct dentry *dentry) |
| { |
| struct inode *inode = dentry->d_inode; |
| |
| return inode && IS_WHITEOUT(inode); |
| } |
| |
| static bool ovl_is_opaquedir(struct dentry *dentry) |
| { |
| int res; |
| char val; |
| struct inode *inode = dentry->d_inode; |
| |
| if (!S_ISDIR(inode->i_mode) || !inode->i_op->getxattr) |
| return false; |
| |
| res = inode->i_op->getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1); |
| if (res == 1 && val == 'y') |
| return true; |
| |
| return false; |
| } |
| |
| static void ovl_dentry_release(struct dentry *dentry) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| |
| if (oe) { |
| unsigned int i; |
| |
| dput(oe->__upperdentry); |
| for (i = 0; i < oe->numlower; i++) |
| dput(oe->lowerstack[i].dentry); |
| kfree_rcu(oe, rcu); |
| } |
| } |
| |
| static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| unsigned int i; |
| int ret = 1; |
| |
| for (i = 0; i < oe->numlower; i++) { |
| struct dentry *d = oe->lowerstack[i].dentry; |
| |
| if (d->d_flags & DCACHE_OP_REVALIDATE) { |
| ret = d->d_op->d_revalidate(d, flags); |
| if (ret < 0) |
| return ret; |
| if (!ret) { |
| if (!(flags & LOOKUP_RCU)) |
| d_invalidate(d); |
| return -ESTALE; |
| } |
| } |
| } |
| return 1; |
| } |
| |
| static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| unsigned int i; |
| int ret = 1; |
| |
| for (i = 0; i < oe->numlower; i++) { |
| struct dentry *d = oe->lowerstack[i].dentry; |
| |
| if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) { |
| ret = d->d_op->d_weak_revalidate(d, flags); |
| if (ret <= 0) |
| break; |
| } |
| } |
| return ret; |
| } |
| |
| static const struct dentry_operations ovl_dentry_operations = { |
| .d_release = ovl_dentry_release, |
| .d_select_inode = ovl_d_select_inode, |
| }; |
| |
| static const struct dentry_operations ovl_reval_dentry_operations = { |
| .d_release = ovl_dentry_release, |
| .d_revalidate = ovl_dentry_revalidate, |
| .d_weak_revalidate = ovl_dentry_weak_revalidate, |
| }; |
| |
| static struct ovl_entry *ovl_alloc_entry(unsigned int numlower) |
| { |
| size_t size = offsetof(struct ovl_entry, lowerstack[numlower]); |
| struct ovl_entry *oe = kzalloc(size, GFP_KERNEL); |
| |
| if (oe) |
| oe->numlower = numlower; |
| |
| return oe; |
| } |
| |
| static bool ovl_dentry_remote(struct dentry *dentry) |
| { |
| return dentry->d_flags & |
| (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE); |
| } |
| |
| static bool ovl_dentry_weird(struct dentry *dentry) |
| { |
| return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT | |
| DCACHE_MANAGE_TRANSIT | |
| DCACHE_OP_HASH | |
| DCACHE_OP_COMPARE); |
| } |
| |
| static inline struct dentry *ovl_lookup_real(struct dentry *dir, |
| struct qstr *name) |
| { |
| struct dentry *dentry; |
| |
| mutex_lock(&dir->d_inode->i_mutex); |
| dentry = lookup_one_len(name->name, dir, name->len); |
| mutex_unlock(&dir->d_inode->i_mutex); |
| |
| if (IS_ERR(dentry)) { |
| if (PTR_ERR(dentry) == -ENOENT) |
| dentry = NULL; |
| } else if (!dentry->d_inode) { |
| dput(dentry); |
| dentry = NULL; |
| } else if (ovl_dentry_weird(dentry)) { |
| dput(dentry); |
| /* Don't support traversing automounts and other weirdness */ |
| dentry = ERR_PTR(-EREMOTE); |
| } |
| return dentry; |
| } |
| |
| /* |
| * Returns next layer in stack starting from top. |
| * Returns -1 if this is the last layer. |
| */ |
| int ovl_path_next(int idx, struct dentry *dentry, struct path *path) |
| { |
| struct ovl_entry *oe = dentry->d_fsdata; |
| |
| BUG_ON(idx < 0); |
| if (idx == 0) { |
| ovl_path_upper(dentry, path); |
| if (path->dentry) |
| return oe->numlower ? 1 : -1; |
| idx++; |
| } |
| BUG_ON(idx > oe->numlower); |
| *path = oe->lowerstack[idx - 1]; |
| |
| return (idx < oe->numlower) ? idx + 1 : -1; |
| } |
| |
| struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, |
| unsigned int flags) |
| { |
| struct ovl_entry *oe; |
| struct ovl_entry *poe = dentry->d_parent->d_fsdata; |
| struct path *stack = NULL; |
| struct dentry *upperdir, *upperdentry = NULL; |
| unsigned int ctr = 0; |
| struct inode *inode = NULL; |
| bool upperopaque = false; |
| struct dentry *this, *prev = NULL; |
| unsigned int i; |
| int err; |
| |
| upperdir = ovl_upperdentry_dereference(poe); |
| if (upperdir) { |
| this = ovl_lookup_real(upperdir, &dentry->d_name); |
| err = PTR_ERR(this); |
| if (IS_ERR(this)) |
| goto out; |
| |
| if (this) { |
| if (unlikely(ovl_dentry_remote(this))) { |
| dput(this); |
| err = -EREMOTE; |
| goto out; |
| } |
| if (ovl_is_whiteout(this)) { |
| dput(this); |
| this = NULL; |
| upperopaque = true; |
| } else if (poe->numlower && ovl_is_opaquedir(this)) { |
| upperopaque = true; |
| } |
| } |
| upperdentry = prev = this; |
| } |
| |
| if (!upperopaque && poe->numlower) { |
| err = -ENOMEM; |
| stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL); |
| if (!stack) |
| goto out_put_upper; |
| } |
| |
| for (i = 0; !upperopaque && i < poe->numlower; i++) { |
| bool opaque = false; |
| struct path lowerpath = poe->lowerstack[i]; |
| |
| this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name); |
| err = PTR_ERR(this); |
| if (IS_ERR(this)) { |
| /* |
| * If it's positive, then treat ENAMETOOLONG as ENOENT. |
| */ |
| if (err == -ENAMETOOLONG && (upperdentry || ctr)) |
| continue; |
| goto out_put; |
| } |
| if (!this) |
| continue; |
| if (ovl_is_whiteout(this)) { |
| dput(this); |
| break; |
| } |
| /* |
| * Only makes sense to check opaque dir if this is not the |
| * lowermost layer. |
| */ |
| if (i < poe->numlower - 1 && ovl_is_opaquedir(this)) |
| opaque = true; |
| |
| if (prev && (!S_ISDIR(prev->d_inode->i_mode) || |
| !S_ISDIR(this->d_inode->i_mode))) { |
| /* |
| * FIXME: check for upper-opaqueness maybe better done |
| * in remove code. |
| */ |
| if (prev == upperdentry) |
| upperopaque = true; |
| dput(this); |
| break; |
| } |
| /* |
| * If this is a non-directory then stop here. |
| */ |
| if (!S_ISDIR(this->d_inode->i_mode)) |
| opaque = true; |
| |
| stack[ctr].dentry = this; |
| stack[ctr].mnt = lowerpath.mnt; |
| ctr++; |
| prev = this; |
| if (opaque) |
| break; |
| } |
| |
| oe = ovl_alloc_entry(ctr); |
| err = -ENOMEM; |
| if (!oe) |
| goto out_put; |
| |
| if (upperdentry || ctr) { |
| struct dentry *realdentry; |
| |
| realdentry = upperdentry ? upperdentry : stack[0].dentry; |
| |
| err = -ENOMEM; |
| inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode, |
| oe); |
| if (!inode) |
| goto out_free_oe; |
| ovl_copyattr(realdentry->d_inode, inode); |
| } |
| |
| oe->opaque = upperopaque; |
| oe->__upperdentry = upperdentry; |
| memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr); |
| kfree(stack); |
| dentry->d_fsdata = oe; |
| d_add(dentry, inode); |
| |
| return NULL; |
| |
| out_free_oe: |
| kfree(oe); |
| out_put: |
| for (i = 0; i < ctr; i++) |
| dput(stack[i].dentry); |
| kfree(stack); |
| out_put_upper: |
| dput(upperdentry); |
| out: |
| return ERR_PTR(err); |
| } |
| |
| struct file *ovl_path_open(struct path *path, int flags) |
| { |
| return dentry_open(path, flags, current_cred()); |
| } |
| |
| static void ovl_put_super(struct super_block *sb) |
| { |
| struct ovl_fs *ufs = sb->s_fs_info; |
| unsigned i; |
| |
| dput(ufs->workdir); |
| mntput(ufs->upper_mnt); |
| for (i = 0; i < ufs->numlower; i++) |
| mntput(ufs->lower_mnt[i]); |
| kfree(ufs->lower_mnt); |
| |
| kfree(ufs->config.lowerdir); |
| kfree(ufs->config.upperdir); |
| kfree(ufs->config.workdir); |
| kfree(ufs); |
| } |
| |
| /** |
| * ovl_statfs |
| * @sb: The overlayfs super block |
| * @buf: The struct kstatfs to fill in with stats |
| * |
| * Get the filesystem statistics. As writes always target the upper layer |
| * filesystem pass the statfs to the upper filesystem (if it exists) |
| */ |
| static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf) |
| { |
| struct ovl_fs *ofs = dentry->d_sb->s_fs_info; |
| struct dentry *root_dentry = dentry->d_sb->s_root; |
| struct path path; |
| int err; |
| |
| ovl_path_real(root_dentry, &path); |
| |
| err = vfs_statfs(&path, buf); |
| if (!err) { |
| buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen); |
| buf->f_type = OVERLAYFS_SUPER_MAGIC; |
| } |
| |
| return err; |
| } |
| |
| /** |
| * ovl_show_options |
| * |
| * Prints the mount options for a given superblock. |
| * Returns zero; does not fail. |
| */ |
| static int ovl_show_options(struct seq_file *m, struct dentry *dentry) |
| { |
| struct super_block *sb = dentry->d_sb; |
| struct ovl_fs *ufs = sb->s_fs_info; |
| |
| seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir); |
| if (ufs->config.upperdir) { |
| seq_printf(m, ",upperdir=%s", ufs->config.upperdir); |
| seq_printf(m, ",workdir=%s", ufs->config.workdir); |
| } |
| return 0; |
| } |
| |
| static int ovl_remount(struct super_block *sb, int *flags, char *data) |
| { |
| struct ovl_fs *ufs = sb->s_fs_info; |
| |
| if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir)) |
| return -EROFS; |
| |
| return 0; |
| } |
| |
| static const struct super_operations ovl_super_operations = { |
| .put_super = ovl_put_super, |
| .statfs = ovl_statfs, |
| .show_options = ovl_show_options, |
| .remount_fs = ovl_remount, |
| }; |
| |
| enum { |
| OPT_LOWERDIR, |
| OPT_UPPERDIR, |
| OPT_WORKDIR, |
| OPT_ERR, |
| }; |
| |
| static const match_table_t ovl_tokens = { |
| {OPT_LOWERDIR, "lowerdir=%s"}, |
| {OPT_UPPERDIR, "upperdir=%s"}, |
| {OPT_WORKDIR, "workdir=%s"}, |
| {OPT_ERR, NULL} |
| }; |
| |
| static char *ovl_next_opt(char **s) |
| { |
| char *sbegin = *s; |
| char *p; |
| |
| if (sbegin == NULL) |
| return NULL; |
| |
| for (p = sbegin; *p; p++) { |
| if (*p == '\\') { |
| p++; |
| if (!*p) |
| break; |
| } else if (*p == ',') { |
| *p = '\0'; |
| *s = p + 1; |
| return sbegin; |
| } |
| } |
| *s = NULL; |
| return sbegin; |
| } |
| |
| static int ovl_parse_opt(char *opt, struct ovl_config *config) |
| { |
| char *p; |
| |
| while ((p = ovl_next_opt(&opt)) != NULL) { |
| int token; |
| substring_t args[MAX_OPT_ARGS]; |
| |
| if (!*p) |
| continue; |
| |
| token = match_token(p, ovl_tokens, args); |
| switch (token) { |
| case OPT_UPPERDIR: |
| kfree(config->upperdir); |
| config->upperdir = match_strdup(&args[0]); |
| if (!config->upperdir) |
| return -ENOMEM; |
| break; |
| |
| case OPT_LOWERDIR: |
| kfree(config->lowerdir); |
| config->lowerdir = match_strdup(&args[0]); |
| if (!config->lowerdir) |
| return -ENOMEM; |
| break; |
| |
| case OPT_WORKDIR: |
| kfree(config->workdir); |
| config->workdir = match_strdup(&args[0]); |
| if (!config->workdir) |
| return -ENOMEM; |
| break; |
| |
| default: |
| pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p); |
| return -EINVAL; |
| } |
| } |
| |
| /* Workdir is useless in non-upper mount */ |
| if (!config->upperdir && config->workdir) { |
| pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n", |
| config->workdir); |
| kfree(config->workdir); |
| config->workdir = NULL; |
| } |
| |
| return 0; |
| } |
| |
| #define OVL_WORKDIR_NAME "work" |
| |
| static struct dentry *ovl_workdir_create(struct vfsmount *mnt, |
| struct dentry *dentry) |
| { |
| struct inode *dir = dentry->d_inode; |
| struct dentry *work; |
| int err; |
| bool retried = false; |
| |
| err = mnt_want_write(mnt); |
| if (err) |
| return ERR_PTR(err); |
| |
| mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT); |
| retry: |
| work = lookup_one_len(OVL_WORKDIR_NAME, dentry, |
| strlen(OVL_WORKDIR_NAME)); |
| |
| if (!IS_ERR(work)) { |
| struct kstat stat = { |
| .mode = S_IFDIR | 0, |
| }; |
| |
| if (work->d_inode) { |
| err = -EEXIST; |
| if (retried) |
| goto out_dput; |
| |
| retried = true; |
| ovl_cleanup(dir, work); |
| dput(work); |
| goto retry; |
| } |
| |
| err = ovl_create_real(dir, work, &stat, NULL, NULL, true); |
| if (err) |
| goto out_dput; |
| } |
| out_unlock: |
| mutex_unlock(&dir->i_mutex); |
| mnt_drop_write(mnt); |
| |
| return work; |
| |
| out_dput: |
| dput(work); |
| work = ERR_PTR(err); |
| goto out_unlock; |
| } |
| |
| static void ovl_unescape(char *s) |
| { |
| char *d = s; |
| |
| for (;; s++, d++) { |
| if (*s == '\\') |
| s++; |
| *d = *s; |
| if (!*s) |
| break; |
| } |
| } |
| |
| static int ovl_mount_dir_noesc(const char *name, struct path *path) |
| { |
| int err = -EINVAL; |
| |
| if (!*name) { |
| pr_err("overlayfs: empty lowerdir\n"); |
| goto out; |
| } |
| err = kern_path(name, LOOKUP_FOLLOW, path); |
| if (err) { |
| pr_err("overlayfs: failed to resolve '%s': %i\n", name, err); |
| goto out; |
| } |
| err = -EINVAL; |
| if (ovl_dentry_weird(path->dentry)) { |
| pr_err("overlayfs: filesystem on '%s' not supported\n", name); |
| goto out_put; |
| } |
| if (!S_ISDIR(path->dentry->d_inode->i_mode)) { |
| pr_err("overlayfs: '%s' not a directory\n", name); |
| goto out_put; |
| } |
| return 0; |
| |
| out_put: |
| path_put(path); |
| out: |
| return err; |
| } |
| |
| static int ovl_mount_dir(const char *name, struct path *path) |
| { |
| int err = -ENOMEM; |
| char *tmp = kstrdup(name, GFP_KERNEL); |
| |
| if (tmp) { |
| ovl_unescape(tmp); |
| err = ovl_mount_dir_noesc(tmp, path); |
| |
| if (!err) |
| if (ovl_dentry_remote(path->dentry)) { |
| pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n", |
| tmp); |
| path_put(path); |
| err = -EINVAL; |
| } |
| kfree(tmp); |
| } |
| return err; |
| } |
| |
| static int ovl_lower_dir(const char *name, struct path *path, long *namelen, |
| int *stack_depth, bool *remote) |
| { |
| int err; |
| struct kstatfs statfs; |
| |
| err = ovl_mount_dir_noesc(name, path); |
| if (err) |
| goto out; |
| |
| err = vfs_statfs(path, &statfs); |
| if (err) { |
| pr_err("overlayfs: statfs failed on '%s'\n", name); |
| goto out_put; |
| } |
| *namelen = max(*namelen, statfs.f_namelen); |
| *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth); |
| |
| if (ovl_dentry_remote(path->dentry)) |
| *remote = true; |
| |
| return 0; |
| |
| out_put: |
| path_put(path); |
| out: |
| return err; |
| } |
| |
| /* Workdir should not be subdir of upperdir and vice versa */ |
| static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir) |
| { |
| bool ok = false; |
| |
| if (workdir != upperdir) { |
| ok = (lock_rename(workdir, upperdir) == NULL); |
| unlock_rename(workdir, upperdir); |
| } |
| return ok; |
| } |
| |
| static unsigned int ovl_split_lowerdirs(char *str) |
| { |
| unsigned int ctr = 1; |
| char *s, *d; |
| |
| for (s = d = str;; s++, d++) { |
| if (*s == '\\') { |
| s++; |
| } else if (*s == ':') { |
| *d = '\0'; |
| ctr++; |
| continue; |
| } |
| *d = *s; |
| if (!*s) |
| break; |
| } |
| return ctr; |
| } |
| |
| static int ovl_fill_super(struct super_block *sb, void *data, int silent) |
| { |
| struct path upperpath = { NULL, NULL }; |
| struct path workpath = { NULL, NULL }; |
| struct dentry *root_dentry; |
| struct ovl_entry *oe; |
| struct ovl_fs *ufs; |
| struct path *stack = NULL; |
| char *lowertmp; |
| char *lower; |
| unsigned int numlower; |
| unsigned int stacklen = 0; |
| unsigned int i; |
| bool remote = false; |
| int err; |
| |
| err = -ENOMEM; |
| ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL); |
| if (!ufs) |
| goto out; |
| |
| err = ovl_parse_opt((char *) data, &ufs->config); |
| if (err) |
| goto out_free_config; |
| |
| err = -EINVAL; |
| if (!ufs->config.lowerdir) { |
| pr_err("overlayfs: missing 'lowerdir'\n"); |
| goto out_free_config; |
| } |
| |
| sb->s_stack_depth = 0; |
| if (ufs->config.upperdir) { |
| if (!ufs->config.workdir) { |
| pr_err("overlayfs: missing 'workdir'\n"); |
| goto out_free_config; |
| } |
| |
| err = ovl_mount_dir(ufs->config.upperdir, &upperpath); |
| if (err) |
| goto out_free_config; |
| |
| /* Upper fs should not be r/o */ |
| if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) { |
| pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n"); |
| err = -EINVAL; |
| goto out_put_upperpath; |
| } |
| |
| err = ovl_mount_dir(ufs->config.workdir, &workpath); |
| if (err) |
| goto out_put_upperpath; |
| |
| err = -EINVAL; |
| if (upperpath.mnt != workpath.mnt) { |
| pr_err("overlayfs: workdir and upperdir must reside under the same mount\n"); |
| goto out_put_workpath; |
| } |
| if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) { |
| pr_err("overlayfs: workdir and upperdir must be separate subtrees\n"); |
| goto out_put_workpath; |
| } |
| sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth; |
| } |
| err = -ENOMEM; |
| lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL); |
| if (!lowertmp) |
| goto out_put_workpath; |
| |
| err = -EINVAL; |
| stacklen = ovl_split_lowerdirs(lowertmp); |
| if (stacklen > OVL_MAX_STACK) { |
| pr_err("overlayfs: too many lower directries, limit is %d\n", |
| OVL_MAX_STACK); |
| goto out_free_lowertmp; |
| } else if (!ufs->config.upperdir && stacklen == 1) { |
| pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n"); |
| goto out_free_lowertmp; |
| } |
| |
| stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL); |
| if (!stack) |
| goto out_free_lowertmp; |
| |
| lower = lowertmp; |
| for (numlower = 0; numlower < stacklen; numlower++) { |
| err = ovl_lower_dir(lower, &stack[numlower], |
| &ufs->lower_namelen, &sb->s_stack_depth, |
| &remote); |
| if (err) |
| goto out_put_lowerpath; |
| |
| lower = strchr(lower, '\0') + 1; |
| } |
| |
| err = -EINVAL; |
| sb->s_stack_depth++; |
| if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { |
| pr_err("overlayfs: maximum fs stacking depth exceeded\n"); |
| goto out_put_lowerpath; |
| } |
| |
| if (ufs->config.upperdir) { |
| ufs->upper_mnt = clone_private_mount(&upperpath); |
| err = PTR_ERR(ufs->upper_mnt); |
| if (IS_ERR(ufs->upper_mnt)) { |
| pr_err("overlayfs: failed to clone upperpath\n"); |
| goto out_put_lowerpath; |
| } |
| |
| ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry); |
| err = PTR_ERR(ufs->workdir); |
| if (IS_ERR(ufs->workdir)) { |
| pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n", |
| ufs->config.workdir, OVL_WORKDIR_NAME, -err); |
| sb->s_flags |= MS_RDONLY; |
| ufs->workdir = NULL; |
| } |
| } |
| |
| err = -ENOMEM; |
| ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL); |
| if (ufs->lower_mnt == NULL) |
| goto out_put_workdir; |
| for (i = 0; i < numlower; i++) { |
| struct vfsmount *mnt = clone_private_mount(&stack[i]); |
| |
| err = PTR_ERR(mnt); |
| if (IS_ERR(mnt)) { |
| pr_err("overlayfs: failed to clone lowerpath\n"); |
| goto out_put_lower_mnt; |
| } |
| /* |
| * Make lower_mnt R/O. That way fchmod/fchown on lower file |
| * will fail instead of modifying lower fs. |
| */ |
| mnt->mnt_flags |= MNT_READONLY; |
| |
| ufs->lower_mnt[ufs->numlower] = mnt; |
| ufs->numlower++; |
| } |
| |
| /* If the upper fs is nonexistent, we mark overlayfs r/o too */ |
| if (!ufs->upper_mnt) |
| sb->s_flags |= MS_RDONLY; |
| |
| if (remote) |
| sb->s_d_op = &ovl_reval_dentry_operations; |
| else |
| sb->s_d_op = &ovl_dentry_operations; |
| |
| err = -ENOMEM; |
| oe = ovl_alloc_entry(numlower); |
| if (!oe) |
| goto out_put_lower_mnt; |
| |
| root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, oe)); |
| if (!root_dentry) |
| goto out_free_oe; |
| |
| mntput(upperpath.mnt); |
| for (i = 0; i < numlower; i++) |
| mntput(stack[i].mnt); |
| path_put(&workpath); |
| kfree(lowertmp); |
| |
| oe->__upperdentry = upperpath.dentry; |
| for (i = 0; i < numlower; i++) { |
| oe->lowerstack[i].dentry = stack[i].dentry; |
| oe->lowerstack[i].mnt = ufs->lower_mnt[i]; |
| } |
| kfree(stack); |
| |
| root_dentry->d_fsdata = oe; |
| |
| sb->s_magic = OVERLAYFS_SUPER_MAGIC; |
| sb->s_op = &ovl_super_operations; |
| sb->s_root = root_dentry; |
| sb->s_fs_info = ufs; |
| |
| return 0; |
| |
| out_free_oe: |
| kfree(oe); |
| out_put_lower_mnt: |
| for (i = 0; i < ufs->numlower; i++) |
| mntput(ufs->lower_mnt[i]); |
| kfree(ufs->lower_mnt); |
| out_put_workdir: |
| dput(ufs->workdir); |
| mntput(ufs->upper_mnt); |
| out_put_lowerpath: |
| for (i = 0; i < numlower; i++) |
| path_put(&stack[i]); |
| kfree(stack); |
| out_free_lowertmp: |
| kfree(lowertmp); |
| out_put_workpath: |
| path_put(&workpath); |
| out_put_upperpath: |
| path_put(&upperpath); |
| out_free_config: |
| kfree(ufs->config.lowerdir); |
| kfree(ufs->config.upperdir); |
| kfree(ufs->config.workdir); |
| kfree(ufs); |
| out: |
| return err; |
| } |
| |
| static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags, |
| const char *dev_name, void *raw_data) |
| { |
| return mount_nodev(fs_type, flags, raw_data, ovl_fill_super); |
| } |
| |
| static struct file_system_type ovl_fs_type = { |
| .owner = THIS_MODULE, |
| .name = "overlay", |
| .mount = ovl_mount, |
| .kill_sb = kill_anon_super, |
| }; |
| MODULE_ALIAS_FS("overlay"); |
| |
| static int __init ovl_init(void) |
| { |
| return register_filesystem(&ovl_fs_type); |
| } |
| |
| static void __exit ovl_exit(void) |
| { |
| unregister_filesystem(&ovl_fs_type); |
| } |
| |
| module_init(ovl_init); |
| module_exit(ovl_exit); |