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    Subject[PATCH 3.2 047/140] nfsd: auth: Fix gid sorting when rootsquash enabled
    3.2.100-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    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>
    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
    @@ -60,10 +60,10 @@ 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);
    }
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