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gro: Fix use after free in tcp_gro_receive

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After calling skb_gro_receive skb->len can no longer be relied
on since if the skb was merged using frags, then its pages will
have been removed and the length reduced.

This caused tcp_gro_receive to prematurely end merging which
resulted in suboptimal performance with ixgbe.

The fix is to store skb->len on the stack.

Reported-by: Mark Wagner <mwagner@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2009-04-17 02:34:38 -07:00 committed by David S. Miller
parent 9dd014eb98
commit a0a69a0106
1 changed files with 4 additions and 2 deletions
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6
net/ipv4/tcp.c
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@ -2511,6 +2511,7 @@ struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
struct sk_buff *p;
struct tcphdr *th;
struct tcphdr *th2;
unsigned int len;
unsigned int thlen;
unsigned int flags;
unsigned int mss = 1;
@ -2531,6 +2532,7 @@ struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
skb_gro_pull(skb, thlen);
len = skb_gro_len(skb);
flags = tcp_flag_word(th);
for (; (p = *head); head = &p->next) {
@ -2561,7 +2563,7 @@ found:
mss = skb_shinfo(p)->gso_size;
flush |= (skb_gro_len(skb) > mss) | !skb_gro_len(skb);
flush |= (len > mss) | !len;
flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
if (flush || skb_gro_receive(head, skb)) {
@ -2574,7 +2576,7 @@ found:
tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
out_check_final:
flush = skb_gro_len(skb) < mss;
flush = len < mss;
flush |= flags & (TCP_FLAG_URG | TCP_FLAG_PSH | TCP_FLAG_RST |
TCP_FLAG_SYN | TCP_FLAG_FIN);