linux-kernel - [ 039/105] pktgen: fix crash when generating IPv6 packets

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Message-Id: <20121028231549.148020010@decadent.org.uk>
Date:	Sun, 28 Oct 2012 23:16:15 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Amerigo Wang <amwang@...hat.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 039/105] pktgen: fix crash when generating IPv6 packets

3.2-stable review patch.  If anyone has any objections, please let me know.

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

From: Amerigo Wang <amwang@...hat.com>

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 <davem@...emloft.net>
Signed-off-by: Cong Wang <amwang@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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);


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