tcp: fix skb_availroom()
Chrome OS team reported a crash on a Pixel ChromeBook in TCP stack : https://code.google.com/p/chromium/issues/detail?id=182056 commita21d45726a
(tcp: avoid order-1 allocations on wifi and tx path) did a poor choice adding an 'avail_size' field to skb, while what we really needed was a 'reserved_tailroom' one. It would have avoided commit22b4a4f22d
(tcp: fix retransmit of partially acked frames) and this commit. Crash occurs because skb_split() is not aware of the 'avail_size' management (and should not be aware) Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Mukesh Agrawal <quiche@chromium.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -500,7 +500,7 @@ struct sk_buff {
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union {
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__u32 mark;
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__u32 dropcount;
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__u32 avail_size;
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__u32 reserved_tailroom;
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};
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sk_buff_data_t inner_transport_header;
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@ -1447,7 +1447,10 @@ static inline int skb_tailroom(const struct sk_buff *skb)
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*/
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static inline int skb_availroom(const struct sk_buff *skb)
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{
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return skb_is_nonlinear(skb) ? 0 : skb->avail_size - skb->len;
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if (skb_is_nonlinear(skb))
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return 0;
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return skb->end - skb->tail - skb->reserved_tailroom;
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}
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/**
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@ -775,7 +775,7 @@ struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp)
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* Make sure that we have exactly size bytes
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* available to the caller, no more, no less.
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*/
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skb->avail_size = size;
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skb->reserved_tailroom = skb->end - skb->tail - size;
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return skb;
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}
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__kfree_skb(skb);
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@ -1298,7 +1298,6 @@ static void __pskb_trim_head(struct sk_buff *skb, int len)
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eat = min_t(int, len, skb_headlen(skb));
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if (eat) {
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__skb_pull(skb, eat);
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skb->avail_size -= eat;
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len -= eat;
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if (!len)
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return;
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