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Commit 60359741 authored by Ian Kent's avatar Ian Kent Committed by Al Viro
Browse files

autofs: use path_has_submounts() to fix unreliable have_submount() checks 

If an automount mount is clone(2)ed into a file system that is propagation
private, when it later expires in the originating namespace, subsequent
calls to autofs ->d_automount() for that dentry in the original namespace
will return ELOOP until the mount is umounted in the cloned namespace.

Now that a struct path is available where needed use path_has_submounts()
instead of have_submounts() so we don't get false positives when checking
if a dentry is a mount point or contains mounts in the current namespace.

Link: http://lkml.kernel.org/r/20161011053423.27645.91233.stgit@pluto.themaw.net


Signed-off-by: default avatarIan Kent <raven@themaw.net>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Omar Sandoval <osandov@osandov.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent cfaf86ab

fs/autofs4/dev-ioctl.c

+1 −1
Original line number Diff line number Diff line
@@ -575,7 +575,7 @@ static int autofs_dev_ioctl_ismountpoint(struct file *fp, 


		devid = new_encode_dev(dev);



		err = have_submounts(path.dentry);

		err = path_has_submounts(&path);



		if (follow_down_one(&path))

			magic = path.dentry->d_sb->s_magic;

fs/autofs4/root.c

+7 −7
Original line number Diff line number Diff line
@@ -384,16 +384,16 @@ static struct vfsmount *autofs4_d_automount(struct path *path) 
		/*

		 * It's possible that user space hasn't removed directories

		 * after umounting a rootless multi-mount, although it

		 * should. For v5 have_submounts() is sufficient to handle

		 * this because the leaves of the directory tree under the

		 * mount never trigger mounts themselves (they have an autofs

		 * trigger mount mounted on them). But v4 pseudo direct mounts

		 * do need the leaves to trigger mounts. In this case we

		 * have no choice but to use the list_empty() check and

		 * should. For v5 path_has_submounts() is sufficient to

		 * handle this because the leaves of the directory tree under

		 * the mount never trigger mounts themselves (they have an

		 * autofs trigger mount mounted on them). But v4 pseudo direct

		 * mounts do need the leaves to trigger mounts. In this case

		 * we have no choice but to use the list_empty() check and

		 * require user space behave.

		 */

		if (sbi->version > 4) {

			if (have_submounts(dentry)) {

			if (path_has_submounts(path)) {

				spin_unlock(&sbi->fs_lock);

				goto done;

			}

fs/autofs4/waitq.c

+7 −3
Original line number Diff line number Diff line
@@ -250,8 +250,9 @@ autofs4_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr) 
static int validate_request(struct autofs_wait_queue **wait,

			    struct autofs_sb_info *sbi,

			    const struct qstr *qstr,

			    struct dentry *dentry, enum autofs_notify notify)

			    const struct path *path, enum autofs_notify notify)

{

	struct dentry *dentry = path->dentry;

	struct autofs_wait_queue *wq;

	struct autofs_info *ino;
@@ -314,6 +315,7 @@ static int validate_request(struct autofs_wait_queue **wait, 
	 */

	if (notify == NFY_MOUNT) {

		struct dentry *new = NULL;

		struct path this;

		int valid = 1;



		/*
@@ -333,7 +335,9 @@ static int validate_request(struct autofs_wait_queue **wait, 
					dentry = new;

			}

		}

		if (have_submounts(dentry))

		this.mnt = path->mnt;

		this.dentry = dentry;

		if (path_has_submounts(&this))

			valid = 0;



		if (new)
@@ -406,7 +410,7 @@ int autofs4_wait(struct autofs_sb_info *sbi, 
		return -EINTR;

	}



	ret = validate_request(&wq, sbi, &qstr, dentry, notify);

	ret = validate_request(&wq, sbi, &qstr, path, notify);

	if (ret <= 0) {

		if (ret != -EINTR)

			mutex_unlock(&sbi->wq_mutex);