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autofs4 - use simple_empty() for empty directory check

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For direct (and offset) mounts, if an automounted mount is manually
umounted the trigger mount dentry can appear non-empty causing it to
not trigger mounts. This can also happen if there is a file handle
leak in a user space automounting application.

This happens because, when a ioctl control file handle is opened
on the mount, a cursor dentry is created which causes list_empty()
to see the dentry as non-empty. Since there is a case where listing
the directory of these dentrys is needed, the use of dcache_dir_*()
functions for .open() and .release() is needed.

Consequently simple_empty() must be used instead of list_empty()
when checking for an empty directory.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ian Kent 2012-12-14 10:23:29 +08:00 committed by Linus Torvalds
parent f55fb0c243
commit 0259cb02c4
1 changed files with 5 additions and 17 deletions
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22
fs/autofs4/root.c
View file

@ -124,13 +124,10 @@ static int autofs4_dir_open(struct inode *inode, struct file *file)
* it.
*/
spin_lock(&sbi->lookup_lock);
spin_lock(&dentry->d_lock);
if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
spin_unlock(&dentry->d_lock);
if (!d_mountpoint(dentry) && simple_empty(dentry)) {
spin_unlock(&sbi->lookup_lock);
return -ENOENT;
}
spin_unlock(&dentry->d_lock);
spin_unlock(&sbi->lookup_lock);
out:
@ -386,12 +383,8 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
goto done;
}
} else {
spin_lock(&dentry->d_lock);
if (!list_empty(&dentry->d_subdirs)) {
spin_unlock(&dentry->d_lock);
if (!simple_empty(dentry))
goto done;
}
spin_unlock(&dentry->d_lock);
}
ino->flags |= AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
@ -610,9 +603,7 @@ static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
spin_lock(&sbi->lookup_lock);
__autofs4_add_expiring(dentry);
spin_lock(&dentry->d_lock);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
d_drop(dentry);
spin_unlock(&sbi->lookup_lock);
return 0;
@ -683,15 +674,12 @@ static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
return -EACCES;
spin_lock(&sbi->lookup_lock);
spin_lock(&dentry->d_lock);
if (!list_empty(&dentry->d_subdirs)) {
spin_unlock(&dentry->d_lock);
if (!simple_empty(dentry)) {
spin_unlock(&sbi->lookup_lock);
return -ENOTEMPTY;
}
__autofs4_add_expiring(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
d_drop(dentry);
spin_unlock(&sbi->lookup_lock);
if (sbi->version < 5)