forked from luck/tmp_suning_uos_patched
tcp: must unclone packets before mangling them
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>
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@ -986,6 +986,9 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
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static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
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unsigned int mss_now)
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{
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/* Make sure we own this skb before messing gso_size/gso_segs */
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WARN_ON_ONCE(skb_cloned(skb));
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if (skb->len <= mss_now || !sk_can_gso(sk) ||
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skb->ip_summed == CHECKSUM_NONE) {
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/* Avoid the costly divide in the normal
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@ -1067,9 +1070,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
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if (nsize < 0)
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nsize = 0;
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if (skb_cloned(skb) &&
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skb_is_nonlinear(skb) &&
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pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
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if (skb_unclone(skb, GFP_ATOMIC))
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return -ENOMEM;
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/* Get a new skb... force flag on. */
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@ -2344,6 +2345,8 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
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int oldpcount = tcp_skb_pcount(skb);
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if (unlikely(oldpcount > 1)) {
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if (skb_unclone(skb, GFP_ATOMIC))
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return -ENOMEM;
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tcp_init_tso_segs(sk, skb, cur_mss);
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tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
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}
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