Patch "nfsd: auth: Fix gid sorting when rootsquash enabled" has been added to the 4.14-stable tree

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

nfsd: auth: Fix gid sorting when rootsquash enabled

to the 4.14-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:
nfsd-auth-fix-gid-sorting-when-rootsquash-enabled.patch
and it can be found in the queue-4.14 subdirectory.

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

From: Ben Hutchings <[email protected]>
Date: Mon, 22 Jan 2018 20:11:06 +0000
Subject: nfsd: auth: Fix gid sorting when rootsquash enabled

From: Ben Hutchings <[email protected]>

commit 1995266727fa8143897e89b55f5d3c79aa828420 upstream.

Commit bdcf0a423ea1 ("kernel: make groups_sort calling a responsibility group_info allocators") appears to break nfsd rootsquash in a pretty major way.

It adds a call to groups_sort() inside the loop that copies/squashes gids, which means the valid gids are sorted along with the following garbage. The net result is that the highest numbered valid gids are replaced with any lower-valued garbage gids, possibly including 0.

We should sort only once, after filling in all the gids.

---
 fs/nfsd/auth.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -60,10 +60,10 @@ int nfsd_setuser(struct svc_rqst *rqstp,
 				gi->gid[i] = exp->ex_anon_gid;
 			else
 				gi->gid[i] = rqgi->gid[i];
-
-			/* Each thread allocates its own gi, no race */
-			groups_sort(gi);
 		}
+
+		/* Each thread allocates its own gi, no race */
+		groups_sort(gi);
 	} else {
 		gi = get_group_info(rqgi);
 	}

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

queue-4.14/ipv6-fix-getsockopt-for-sockets-with-default-ipv6_autoflowlabel.patch queue-4.14/nfsd-auth-fix-gid-sorting-when-rootsquash-enabled.patch