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Commit c9ffec48 authored by Ian Kent's avatar Ian Kent Committed by Linus Torvalds
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[PATCH] autofs4: check for directory re-create in lookup 



This problem was identified and fixed some time ago by Jeff Moyer but it fell
through the cracks somehow.

It is possible that a user space application could remove and re-create a
directory during a request.  To avoid returning a failure from lookup
incorrectly when our current dentry is unhashed we need to check if another
positive, hashed dentry matching this one exists and if so return it instead
of a fail.

Signed-off-by: default avatarJeff Moyer <jmoyer@redhat.com>
Signed-off-by: default avatarIan Kent <raven@themaw.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f50b6f86

fs/autofs4/root.c

+19 −4
Original line number Diff line number Diff line
@@ -655,14 +655,29 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s 


	/*

	 * If this dentry is unhashed, then we shouldn't honour this

	 * lookup even if the dentry is positive.  Returning ENOENT here

	 * doesn't do the right thing for all system calls, but it should

	 * be OK for the operations we permit from an autofs.

	 * lookup.  Returning ENOENT here doesn't do the right thing

	 * for all system calls, but it should be OK for the operations

	 * we permit from an autofs.

	 */

	if (dentry->d_inode && d_unhashed(dentry)) {

		/*

		 * A user space application can (and has done in the past)

		 * remove and re-create this directory during the callback.

		 * This can leave us with an unhashed dentry, but a

		 * successful mount!  So we need to perform another

		 * cached lookup in case the dentry now exists.

		 */

		struct dentry *parent = dentry->d_parent;

		struct dentry *new = d_lookup(parent, &dentry->d_name);

		if (new != NULL)

			dentry = new;

		else

			dentry = ERR_PTR(-ENOENT);



		if (unhashed)

			dput(unhashed);

		return ERR_PTR(-ENOENT);



		return dentry;

	}



	if (unhashed)