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Commit 0259cb02 authored by Ian Kent's avatar Ian Kent Committed by Linus Torvalds
Browse files

autofs4 - use simple_empty() for empty directory check 



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: default avatarIan Kent <raven@themaw.net>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f55fb0c2

fs/autofs4/root.c

+5 −17
Original line number Diff line number Diff line
@@ -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:
@@ -386,13 +383,9 @@ 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);

		status = autofs4_mount_wait(dentry);
@@ -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)