Fix rmmod/read/write races in /proc entries
Fix following races:
===========================================
1. Write via ->write_proc sleeps in copy_from_user(). Module disappears
meanwhile. Or, more generically, system call done on /proc file, method
supplied by module is called, module dissapeares meanwhile.
pde = create_proc_entry()
if (!pde)
return -ENOMEM;
pde->write_proc = ...
open
write
copy_from_user
pde = create_proc_entry();
if (!pde) {
remove_proc_entry();
return -ENOMEM;
/* module unloaded */
}
*boom*
==========================================
2. bogo-revoke aka proc_kill_inodes()
remove_proc_entry vfs_read
proc_kill_inodes [check ->f_op validness]
[check ->f_op->read validness]
[verify_area, security permissions checks]
->f_op = NULL;
if (file->f_op->read)
/* ->f_op dereference, boom */
NOTE, NOTE, NOTE: file_operations are proxied for regular files only. Let's
see how this scheme behaves, then extend if needed for directories.
Directories creators in /proc only set ->owner for them, so proxying for
directories may be unneeded.
NOTE, NOTE, NOTE: methods being proxied are ->llseek, ->read, ->write,
->poll, ->unlocked_ioctl, ->ioctl, ->compat_ioctl, ->open, ->release.
If your in-tree module uses something else, yell on me. Full audit pending.
[akpm@linux-foundation.org: build fix]
Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index d5ce65c..dd28e86 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -10,6 +10,7 @@
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
+#include <linux/completion.h>
#include <linux/file.h>
#include <linux/limits.h>
#include <linux/init.h>
@@ -140,6 +141,251 @@
.remount_fs = proc_remount,
};
+static void pde_users_dec(struct proc_dir_entry *pde)
+{
+ spin_lock(&pde->pde_unload_lock);
+ pde->pde_users--;
+ if (pde->pde_unload_completion && pde->pde_users == 0)
+ complete(pde->pde_unload_completion);
+ spin_unlock(&pde->pde_unload_lock);
+}
+
+static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
+{
+ struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
+ loff_t rv = -EINVAL;
+ loff_t (*llseek)(struct file *, loff_t, int);
+
+ spin_lock(&pde->pde_unload_lock);
+ /*
+ * remove_proc_entry() is going to delete PDE (as part of module
+ * cleanup sequence). No new callers into module allowed.
+ */
+ if (!pde->proc_fops) {
+ spin_unlock(&pde->pde_unload_lock);
+ return rv;
+ }
+ /*
+ * Bump refcount so that remove_proc_entry will wail for ->llseek to
+ * complete.
+ */
+ pde->pde_users++;
+ /*
+ * Save function pointer under lock, to protect against ->proc_fops
+ * NULL'ifying right after ->pde_unload_lock is dropped.
+ */
+ llseek = pde->proc_fops->llseek;
+ spin_unlock(&pde->pde_unload_lock);
+
+ if (!llseek)
+ llseek = default_llseek;
+ rv = llseek(file, offset, whence);
+
+ pde_users_dec(pde);
+ return rv;
+}
+
+static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+ struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
+ ssize_t rv = -EIO;
+ ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
+
+ spin_lock(&pde->pde_unload_lock);
+ if (!pde->proc_fops) {
+ spin_unlock(&pde->pde_unload_lock);
+ return rv;
+ }
+ pde->pde_users++;
+ read = pde->proc_fops->read;
+ spin_unlock(&pde->pde_unload_lock);
+
+ if (read)
+ rv = read(file, buf, count, ppos);
+
+ pde_users_dec(pde);
+ return rv;
+}
+
+static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
+{
+ struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
+ ssize_t rv = -EIO;
+ ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
+
+ spin_lock(&pde->pde_unload_lock);
+ if (!pde->proc_fops) {
+ spin_unlock(&pde->pde_unload_lock);
+ return rv;
+ }
+ pde->pde_users++;
+ write = pde->proc_fops->write;
+ spin_unlock(&pde->pde_unload_lock);
+
+ if (write)
+ rv = write(file, buf, count, ppos);
+
+ pde_users_dec(pde);
+ return rv;
+}
+
+static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
+{
+ struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
+ unsigned int rv = 0;
+ unsigned int (*poll)(struct file *, struct poll_table_struct *);
+
+ spin_lock(&pde->pde_unload_lock);
+ if (!pde->proc_fops) {
+ spin_unlock(&pde->pde_unload_lock);
+ return rv;
+ }
+ pde->pde_users++;
+ poll = pde->proc_fops->poll;
+ spin_unlock(&pde->pde_unload_lock);
+
+ if (poll)
+ rv = poll(file, pts);
+
+ pde_users_dec(pde);
+ return rv;
+}
+
+static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
+ long rv = -ENOTTY;
+ long (*unlocked_ioctl)(struct file *, unsigned int, unsigned long);
+ int (*ioctl)(struct inode *, struct file *, unsigned int, unsigned long);
+
+ spin_lock(&pde->pde_unload_lock);
+ if (!pde->proc_fops) {
+ spin_unlock(&pde->pde_unload_lock);
+ return rv;
+ }
+ pde->pde_users++;
+ unlocked_ioctl = pde->proc_fops->unlocked_ioctl;
+ ioctl = pde->proc_fops->ioctl;
+ spin_unlock(&pde->pde_unload_lock);
+
+ if (unlocked_ioctl) {
+ rv = unlocked_ioctl(file, cmd, arg);
+ if (rv == -ENOIOCTLCMD)
+ rv = -EINVAL;
+ } else if (ioctl) {
+ lock_kernel();
+ rv = ioctl(file->f_path.dentry->d_inode, file, cmd, arg);
+ unlock_kernel();
+ }
+
+ pde_users_dec(pde);
+ return rv;
+}
+
+#ifdef CONFIG_COMPAT
+static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
+ long rv = -ENOTTY;
+ long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
+
+ spin_lock(&pde->pde_unload_lock);
+ if (!pde->proc_fops) {
+ spin_unlock(&pde->pde_unload_lock);
+ return rv;
+ }
+ pde->pde_users++;
+ compat_ioctl = pde->proc_fops->compat_ioctl;
+ spin_unlock(&pde->pde_unload_lock);
+
+ if (compat_ioctl)
+ rv = compat_ioctl(file, cmd, arg);
+
+ pde_users_dec(pde);
+ return rv;
+}
+#endif
+
+static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
+ int rv = -EIO;
+ int (*mmap)(struct file *, struct vm_area_struct *);
+
+ spin_lock(&pde->pde_unload_lock);
+ if (!pde->proc_fops) {
+ spin_unlock(&pde->pde_unload_lock);
+ return rv;
+ }
+ pde->pde_users++;
+ mmap = pde->proc_fops->mmap;
+ spin_unlock(&pde->pde_unload_lock);
+
+ if (mmap)
+ rv = mmap(file, vma);
+
+ pde_users_dec(pde);
+ return rv;
+}
+
+static int proc_reg_open(struct inode *inode, struct file *file)
+{
+ struct proc_dir_entry *pde = PDE(inode);
+ int rv = 0;
+ int (*open)(struct inode *, struct file *);
+
+ spin_lock(&pde->pde_unload_lock);
+ if (!pde->proc_fops) {
+ spin_unlock(&pde->pde_unload_lock);
+ return rv;
+ }
+ pde->pde_users++;
+ open = pde->proc_fops->open;
+ spin_unlock(&pde->pde_unload_lock);
+
+ if (open)
+ rv = open(inode, file);
+
+ pde_users_dec(pde);
+ return rv;
+}
+
+static int proc_reg_release(struct inode *inode, struct file *file)
+{
+ struct proc_dir_entry *pde = PDE(inode);
+ int rv = 0;
+ int (*release)(struct inode *, struct file *);
+
+ spin_lock(&pde->pde_unload_lock);
+ if (!pde->proc_fops) {
+ spin_unlock(&pde->pde_unload_lock);
+ return rv;
+ }
+ pde->pde_users++;
+ release = pde->proc_fops->release;
+ spin_unlock(&pde->pde_unload_lock);
+
+ if (release)
+ rv = release(inode, file);
+
+ pde_users_dec(pde);
+ return rv;
+}
+
+static const struct file_operations proc_reg_file_ops = {
+ .llseek = proc_reg_llseek,
+ .read = proc_reg_read,
+ .write = proc_reg_write,
+ .poll = proc_reg_poll,
+ .unlocked_ioctl = proc_reg_unlocked_ioctl,
+#ifdef CONFIG_COMPAT
+ .compat_ioctl = proc_reg_compat_ioctl,
+#endif
+ .mmap = proc_reg_mmap,
+ .open = proc_reg_open,
+ .release = proc_reg_release,
+};
+
struct inode *proc_get_inode(struct super_block *sb, unsigned int ino,
struct proc_dir_entry *de)
{
@@ -166,8 +412,12 @@
inode->i_nlink = de->nlink;
if (de->proc_iops)
inode->i_op = de->proc_iops;
- if (de->proc_fops)
- inode->i_fop = de->proc_fops;
+ if (de->proc_fops) {
+ if (S_ISREG(inode->i_mode))
+ inode->i_fop = &proc_reg_file_ops;
+ else
+ inode->i_fop = de->proc_fops;
+ }
}
return inode;