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    Subject[ 33/62] pktgen: fix crash when generating IPv6 packets
    Date
    3.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Amerigo Wang <amwang@redhat.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.

    Signed-off-by: Cong Wang <amwang@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    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) -
    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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