kernel/groups.c: fix integer overflow in groups_search

gid_t is a unsigned int.  If group_info contains a gid greater than
MAX_INT, groups_search() function may look on the wrong side of the search
tree.

This solves some unfair "permission denied" problems.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/groups.c b/kernel/groups.c
index 53b1916..253dc0f 100644 (file)
--- a/kernel/groups.c
+++ b/kernel/groups.c
@@ -143,10 +143,9 @@ int groups_search(const struct group_info *group_info, gid_t grp)
        right = group_info->ngroups;
        while (left < right) {
                unsigned int mid = (left+right)/2;
-               int cmp = grp - GROUP_AT(group_info, mid);
-               if (cmp > 0)
+               if (grp > GROUP_AT(group_info, mid))
                        left = mid + 1;
-               else if (cmp < 0)
+               else if (grp < GROUP_AT(group_info, mid))
                        right = mid;
                else
                        return 1;