netfilter: nf_tables: fix oob access

[ 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>

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 2cb429d..120e9ae 100644 (file)
--- 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 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);
        }