Patch "nfsd: auth: Fix gid sorting when rootsquash enabled" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

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 4.9-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-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 1995266727fa8143897e89b55f5d3c79aa828420 Mon Sep 17 00:00:00 2001
From: Ben Hutchings <ben.hutchings@codethink.co.uk>
Date: Mon, 22 Jan 2018 20:11:06 +0000
Subject: nfsd: auth: Fix gid sorting when rootsquash enabled

From: Ben Hutchings <ben.hutchings@codethink.co.uk>

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.

Fixes: bdcf0a423ea1 ("kernel: make groups_sort calling a responsibility ...")
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Acked-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Wolfgang Walter <linux@stwm.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/fs/nfsd/auth.c
+++ b/fs/nfsd/auth.c
@@ -59,10 +59,10 @@ 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 ben.hutchings@codethink.co.uk are

queue-4.9/vsyscall-fix-permissions-for-emulate-mode-with-kaiser-pti.patch
queue-4.9/ipv6-fix-getsockopt-for-sockets-with-default-ipv6_autoflowlabel.patch
queue-4.9/nfsd-auth-fix-gid-sorting-when-rootsquash-enabled.patch