pktgen: fix crash when generating IPv6 packets
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: <stable@vger.kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>