gro: Fix use after free in tcp_gro_receive
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>
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index fafbec8..1d7f49c 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2511,6 +2511,7 @@
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 @@
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 @@
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 @@
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);