[ 33/62] pktgen: fix crash when generating IPv6 packets

From: Greg Kroah-Hartman
Date: Thu Oct 18 2012 - 23:28:21 EST

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


From: Amerigo Wang <amwang@xxxxxxxxxx>

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) -

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.

Signed-off-by: Cong Wang <amwang@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

net/core/pktgen.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -2932,7 +2932,7 @@ static struct sk_buff *fill_packet_ipv6(
sizeof(struct ipv6hdr) - sizeof(struct udphdr) -

- 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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