From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-Id: <20121028231549.148020010@decadent.org.uk> Date: Sun, 28 Oct 2012 23:16:15 +0000 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Amerigo Wang , "David S. Miller" Subject: [ 039/105] pktgen: fix crash when generating IPv6 packets In-Reply-To: <20121028231536.970033833@decadent.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Amerigo Wang commit 5aa8b572007c4bca1e6d3dd4c4820f1ae49d6bb2 upstream. For IPv6, sizeof(struct ipv6hdr) = 40, thus the following expression will result negative: datalen = pkt_dev->cur_pkt_size - 14 - sizeof(struct ipv6hdr) - sizeof(struct udphdr) - pkt_dev->pkt_overhead; And, the check "if (datalen < sizeof(struct pktgen_hdr))" will be passed as "datalen" is promoted to unsigned, therefore will cause a crash later. This is a quick fix by checking if "datalen" is negative. The following patch will increase the default value of 'min_pkt_size' for IPv6. This bug should exist for a long time, so Cc -stable too. Cc: David S. Miller Signed-off-by: Cong Wang Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/core/pktgen.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -2935,7 +2935,7 @@ static struct sk_buff *fill_packet_ipv6( sizeof(struct ipv6hdr) - sizeof(struct udphdr) - pkt_dev->pkt_overhead; - if (datalen < sizeof(struct pktgen_hdr)) { + if (datalen < 0 || datalen < sizeof(struct pktgen_hdr)) { datalen = sizeof(struct pktgen_hdr); if (net_ratelimit()) pr_info("increased datalen to %d\n", datalen);