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    Subject[PATCH 3.12 052/170] ipvs: Fix panic due to non-linear skb
    Date
    From: Peter Christensen <pch@ordbogen.com>

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

    ===============

    commit f44a5f45f544561302e855e7bd104e5f506ec01b upstream.

    Receiving a ICMP response to an IPIP packet in a non-linear skb could
    cause a kernel panic in __skb_pull.

    The problem was introduced in
    commit f2edb9f7706dcb2c0d9a362b2ba849efe3a97f5e ("ipvs: implement
    passive PMTUD for IPIP packets").

    Signed-off-by: Peter Christensen <pch@ordbogen.com>
    Acked-by: Julian Anastasov <ja@ssi.bg>
    Signed-off-by: Simon Horman <horms@verge.net.au>
    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    ---
    net/netfilter/ipvs/ip_vs_core.c | 15 ++++++++++-----
    1 file changed, 10 insertions(+), 5 deletions(-)

    diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
    index 3581736446d5..e2d38e5318d4 100644
    --- a/net/netfilter/ipvs/ip_vs_core.c
    +++ b/net/netfilter/ipvs/ip_vs_core.c
    @@ -1392,15 +1392,19 @@ ip_vs_in_icmp(struct sk_buff *skb, int *related, unsigned int hooknum)

    if (ipip) {
    __be32 info = ic->un.gateway;
    + __u8 type = ic->type;
    + __u8 code = ic->code;

    /* Update the MTU */
    if (ic->type == ICMP_DEST_UNREACH &&
    ic->code == ICMP_FRAG_NEEDED) {
    struct ip_vs_dest *dest = cp->dest;
    u32 mtu = ntohs(ic->un.frag.mtu);
    + __be16 frag_off = cih->frag_off;

    /* Strip outer IP and ICMP, go to IPIP header */
    - __skb_pull(skb, ihl + sizeof(_icmph));
    + if (pskb_pull(skb, ihl + sizeof(_icmph)) == NULL)
    + goto ignore_ipip;
    offset2 -= ihl + sizeof(_icmph);
    skb_reset_network_header(skb);
    IP_VS_DBG(12, "ICMP for IPIP %pI4->%pI4: mtu=%u\n",
    @@ -1408,7 +1412,7 @@ ip_vs_in_icmp(struct sk_buff *skb, int *related, unsigned int hooknum)
    ipv4_update_pmtu(skb, dev_net(skb->dev),
    mtu, 0, 0, 0, 0);
    /* Client uses PMTUD? */
    - if (!(cih->frag_off & htons(IP_DF)))
    + if (!(frag_off & htons(IP_DF)))
    goto ignore_ipip;
    /* Prefer the resulting PMTU */
    if (dest) {
    @@ -1427,12 +1431,13 @@ ip_vs_in_icmp(struct sk_buff *skb, int *related, unsigned int hooknum)
    /* Strip outer IP, ICMP and IPIP, go to IP header of
    * original request.
    */
    - __skb_pull(skb, offset2);
    + if (pskb_pull(skb, offset2) == NULL)
    + goto ignore_ipip;
    skb_reset_network_header(skb);
    IP_VS_DBG(12, "Sending ICMP for %pI4->%pI4: t=%u, c=%u, i=%u\n",
    &ip_hdr(skb)->saddr, &ip_hdr(skb)->daddr,
    - ic->type, ic->code, ntohl(info));
    - icmp_send(skb, ic->type, ic->code, info);
    + type, code, ntohl(info));
    + icmp_send(skb, type, code, info);
    /* ICMP can be shorter but anyways, account it */
    ip_vs_out_stats(cp, skb);

    --
    2.0.0


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