From a0a69a0106dab8d20596f97f6674bed3b394d1ee Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Fri, 17 Apr 2009 02:34:38 -0700 Subject: [PATCH] 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 Signed-off-by: Herbert Xu Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index fafbec8b073e..1d7f49c6f0ca 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -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); -- 2.20.1