3.16.55-rc1 review patch. If anyone has any objections, please let me know.
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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 [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- 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, GROUP_AT(gi, i) = exp->ex_anon_gid; else GROUP_AT(gi, i) = GROUP_AT(rqgi, 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); }