[Xen-changelog] [linux-2.6.18-xen] gso: Ensure that the packet is long enough

["Xen patchbot-linux-2.6.18-xen" <patchbot-linux-2.6.18-xen@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1231941847 0
# Node ID d490aa798cc4efffca3f0dc4bbe41efa9d84e248
# Parent  8081d19dce896687c152a7bacccf2d41c0e4d153
gso: Ensure that the packet is long enough

When we get a GSO packet from an untrusted source, we need to
ensure that it is sufficiently long so that we don't end up
crashing.

Based on discovery and patch by Ian Campbell.

Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 net/ipv4/tcp.c |   13 +++++++------
 1 files changed, 7 insertions(+), 6 deletions(-)

diff -r 8081d19dce89 -r d490aa798cc4 net/ipv4/tcp.c
--- a/net/ipv4/tcp.c    Wed Jan 14 14:03:42 2009 +0000
+++ b/net/ipv4/tcp.c    Wed Jan 14 14:04:07 2009 +0000
@@ -2153,7 +2153,7 @@ struct sk_buff *tcp_tso_segment(struct s
        unsigned int seq;
        unsigned int delta;
        unsigned int oldlen;
-       unsigned int len;
+       unsigned int mss;
 
        if (!pskb_may_pull(skb, sizeof(*th)))
                goto out;
@@ -2169,10 +2169,13 @@ struct sk_buff *tcp_tso_segment(struct s
        oldlen = (u16)~skb->len;
        __skb_pull(skb, thlen);
 
+       mss = skb_shinfo(skb)->gso_size;
+       if (unlikely(skb->len <= mss))
+               goto out;
+
        if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
                /* Packet is from an untrusted source, reset gso_segs. */
                int type = skb_shinfo(skb)->gso_type;
-               int mss;
 
                if (unlikely(type &
                             ~(SKB_GSO_TCPV4 |
@@ -2183,7 +2186,6 @@ struct sk_buff *tcp_tso_segment(struct s
                             !(type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))))
                        goto out;
 
-               mss = skb_shinfo(skb)->gso_size;
                skb_shinfo(skb)->gso_segs = (skb->len + mss - 1) / mss;
 
                segs = NULL;
@@ -2194,8 +2196,7 @@ struct sk_buff *tcp_tso_segment(struct s
        if (IS_ERR(segs))
                goto out;
 
-       len = skb_shinfo(skb)->gso_size;
-       delta = htonl(oldlen + (thlen + len));
+       delta = htonl(oldlen + (thlen + mss));
 
        skb = segs;
        th = skb->h.th;
@@ -2209,7 +2210,7 @@ struct sk_buff *tcp_tso_segment(struct s
                        th->check = csum_fold(csum_partial(skb->h.raw, thlen,
                                                           skb->csum));
 
-               seq += len;
+               seq += mss;
                skb = skb->next;
                th = skb->h.th;
 

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