Patch "Make __xfs_xattr_put_listen preperly report errors." has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

Make __xfs_xattr_put_listen preperly report errors.

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
make-__xfs_xattr_put_listen-preperly-report-errors.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Artem Savkov <[email protected]>
Date: Wed, 14 Sep 2016 07:40:35 +1000
Subject: Make __xfs_xattr_put_listen preperly report errors.

From: Artem Savkov <[email protected]>

commit 791cc43b36eb1f88166c8505900cad1b43c7fe1a upstream.

Commit 2a6fba6 "xfs: only return -errno or success from attr ->put_listent" changes the returnvalue of __xfs_xattr_put_listen to 0 in case when there is insufficient space in the buffer assuming that setting context->count to -1 would be enough, but all of the ->put_listent callers only check seen_enough. This results in a failed assertion:
XFS: Assertion failed: context->count >= 0, file: fs/xfs/xfs_xattr.c, line: 175 in insufficient buffer size case.

This is only reproducible with at least 2 xattrs and only when the buffer gets depleted before the last one.

Furthermore if buffersize is such that it is enough to hold the last xattr's name, but not enough to hold the sum of preceeding xattr names listxattr won't fail with ERANGE, but will suceed returning last xattr's name without the first character. The first character end's up overwriting data stored at (context->alist - 1).

---
 fs/xfs/xfs_xattr.c |    1 +
 1 file changed, 1 insertion(+)

@@ -180,6 +180,7 @@ xfs_xattr_put_listent(
 	arraytop = context->count + prefix_len + namelen + 1;
 	if (arraytop > context->firstu) {
 		context->count = -1;	/* insufficient space */
+		context->seen_enough = 1;
 		return 0;
 	}
 	offset = (char *)context->alist + context->count;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/make-__xfs_xattr_put_listen-preperly-report-errors.patch