From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: [PATCH] af_packet: check loop for greater than zero in tpacket_fill_skb Date: Sun, 10 Jun 2012 21:25:08 +0200 Message-ID: <4FD4F494.6020102@iogearbox.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "netdev@vger.kernel.org" To: "David S. Miller" Return-path: Received: from www62.your-server.de ([213.133.104.62]:35682 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751399Ab2FJTZQ (ORCPT ); Sun, 10 Jun 2012 15:25:16 -0400 Sender: netdev-owner@vger.kernel.org List-ID: It could be more safe to check the 'to_write' for 'greater than zero' instead for 'not zero'. 'to_write' is of type int and subtraction operations are performed on it, so in the case of malformed values that are subtracted from 'to_write', it could become less than zero, which is then interpreted as 'not zero' in the while condition, thus the loop won't return as expected. Signed-off-by: Daniel Borkmann --- net/packet/af_packet.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 0f66174..3e53680 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2027,7 +2027,7 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb, skb->truesize += to_write; atomic_add(to_write, &po->sk.sk_wmem_alloc); - while (likely(to_write)) { + while (likely(to_write > 0)) { nr_frags = skb_shinfo(skb)->nr_frags; if (unlikely(nr_frags >= MAX_SKB_FRAGS)) {