netdev - [PATCH 3/6] netfilter: nf_tables: fix oob access

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Date:   Thu,  5 Jan 2017 12:19:50 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 3/6] netfilter: nf_tables: fix oob access

From: Florian Westphal <fw@...len.de>

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@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_tables_api.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index a019a87e58ee..0db5f9782265 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2115,7 +2115,7 @@ static void nf_tables_rule_destroy(const struct nft_ctx *ctx,
 	 * 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);
 	}
-- 
2.1.4