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 <edumazet@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index dc4d49a..daabf24 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -760,6 +760,16 @@
(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