Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.10 03/54] tcp: must unclone packets before mangling them | Date | Fri, 1 Nov 2013 15:03:31 -0700 |
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3.10-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@google.com>
[ 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> --- net/ipv4/tcp_output.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -976,6 +976,9 @@ static void tcp_queue_skb(struct sock *s static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb, unsigned int mss_now) { + /* Make sure we own this skb before messing gso_size/gso_segs */ + WARN_ON_ONCE(skb_cloned(skb)); + if (skb->len <= mss_now || !sk_can_gso(sk) || skb->ip_summed == CHECKSUM_NONE) { /* Avoid the costly divide in the normal @@ -1057,9 +1060,7 @@ int tcp_fragment(struct sock *sk, struct if (nsize < 0) nsize = 0; - if (skb_cloned(skb) && - skb_is_nonlinear(skb) && - pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) + if (skb_unclone(skb, GFP_ATOMIC)) return -ENOMEM; /* Get a new skb... force flag on. */ @@ -2334,6 +2335,8 @@ int __tcp_retransmit_skb(struct sock *sk int oldpcount = tcp_skb_pcount(skb); if (unlikely(oldpcount > 1)) { + if (skb_unclone(skb, GFP_ATOMIC)) + return -ENOMEM; tcp_init_tso_segs(sk, skb, cur_mss); tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb)); }
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