From 11db1e4cee071defc371d0fc7f1740024fbe5b06 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 15 Oct 2013 11:54:30 -0700 Subject: tcp: must unclone packets before mangling them [ Upstream commit c52e2421f7368fd36cbe330d2cf41b10452e39a9 ] TCP stack should make sure it owns skbs before mangling them. We had various crashes using bnx2x, and it turned out gso_size was cleared right before bnx2x driver was populating TC descriptor of the _previous_ packet send. TCP stack can sometime retransmit packets that are still in Qdisc. Of course we could make bnx2x driver more robust (using ACCESS_ONCE(shinfo->gso_size) for example), but the bug is TCP stack. We have identified two points where skb_unclone() was needed. This patch adds a WARN_ON_ONCE() to warn us if we missed another fix of this kind. Kudos to Neal for finding the root cause of this bug. Its visible using small MSS. Signed-off-by: Eric Dumazet Signed-off-by: Neal Cardwell Cc: Yuchung Cheng Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- include/linux/skbuff.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index dc4d49a0c07d..daabf24655af 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -760,6 +760,16 @@ static inline int skb_cloned(const struct sk_buff *skb) (atomic_read(&skb_shinfo(skb)->dataref) & SKB_DATAREF_MASK) != 1; } +static inline int skb_unclone(struct sk_buff *skb, gfp_t pri) +{ + might_sleep_if(pri & __GFP_WAIT); + + if (skb_cloned(skb)) + return pskb_expand_head(skb, 0, 0, pri); + + return 0; +} + /** * skb_header_cloned - is the header a clone * @skb: buffer to check -- cgit v1.2.3