linux-kernel - [PATCH 3.16 198/305] netfilter: nf

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Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Florian Westphal" <fw@...len.de>,
        "Pablo Neira Ayuso" <pablo@...filter.org>
Subject: [PATCH 3.16 198/305] netfilter: nf_tables: fix oob access

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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

commit 3e38df136e453aa69eb4472108ebce2fb00b1ba6 upstream.

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>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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
@@ -1689,7 +1689,7 @@ 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);
 	}