[PATCH] fix integer overflow in groups_search

[Jerome Marchand <jmarchan@redhat.com>]

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>
---
diff --git a/kernel/groups.c b/kernel/groups.c
index 53b1916..253dc0f 100644
--- 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;