[patch] groups: integer underflow in groups_alloc()

From: Dan Carpenter
Date: Mon Feb 23 2015 - 10:44:41 EST

This is called from rsc_parse() with a use controlled value. Say for
example that "gidsetsize" is negative, then we could end up allocating
less than sizeof(struct group_info) leading to memory corruption.

Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
I copied the NGROUPS_MAX limit from the surrounding code, I'm not
absolutely that it's the correct limit to use.

diff --git a/kernel/groups.c b/kernel/groups.c
index 664411f..e9341b3 100644
--- a/kernel/groups.c
+++ b/kernel/groups.c
@@ -18,6 +18,9 @@ struct group_info *groups_alloc(int gidsetsize)
int nblocks;
int i;

+ if ((unsigned)gidsetsize > NGROUPS_MAX)
+ return NULL;
nblocks = (gidsetsize + NGROUPS_PER_BLOCK - 1) / NGROUPS_PER_BLOCK;
/* Make sure we always allocate at least one indirect block pointer */
nblocks = nblocks ? : 1;
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/