[PATCH 4.4 91/96] netfilter: nf_tables: fix oob access

Greg Kroah-Hartman
2017-11-28T10:32:24Z

From: Florian Westphal <fw@strlen.de>

[ Upstream commit 3e38df136e453aa69eb4472108ebce2fb00b1ba6 ]

BUG: KASAN: slab-out-of-bounds in nf_tables_rule_destroy+0xf1/0x130 at addr ffff88006a4c35c8
Read of size 8 by task nft/1607

When we've destroyed last valid expr, nft_expr_next() returns an invalid expr.
We must not dereference it unless it passes != nft_expr_last() check.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/netfilter/nf_tables_api.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1996,7 +1996,7 @@ static void nf_tables_rule_destroy(const
* is called on error from nf_tables_newrule().
*/
expr = nft_expr_first(rule);
- while (expr->ops && expr != nft_expr_last(rule)) {
+ while (expr != nft_expr_last(rule) && expr->ops) {
nf_tables_expr_destroy(ctx, expr);
expr = nft_expr_next(expr);
}