From 54d431176429e9cf064461589e5174349a9f73da Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Thu, 19 Oct 2017 12:40:39 -0400 Subject: [PATCH] sock: correct sk_wmem_queued accounting on efault in tcp zerocopy Syzkaller hits WARN_ON(sk->sk_wmem_queued) in sk_stream_kill_queues after triggering an EFAULT in __zerocopy_sg_from_iter. On this error, skb_zerocopy_stream_iter resets the skb to its state before the operation with __pskb_trim. It cannot kfree_skb like datagram callers, as the skb may have data from a previous send call. __pskb_trim calls skb_condense for unowned skbs, which adjusts their truesize. These tcp skbuffs are owned and their truesize must add up to sk_wmem_queued. But they match because their skb->sk is NULL until tcp_transmit_skb. Temporarily set skb->sk when calling __pskb_trim to signal that the skbuffs are owned and avoid the skb_condense path. Fixes: 52267790ef52 ("sock: add MSG_ZEROCOPY") Signed-off-by: Willem de Bruijn Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- net/core/skbuff.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index e62476beee95..24656076906d 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1124,9 +1124,13 @@ int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb, err = __zerocopy_sg_from_iter(sk, skb, &msg->msg_iter, len); if (err == -EFAULT || (err == -EMSGSIZE && skb->len == orig_len)) { + struct sock *save_sk = skb->sk; + /* Streams do not free skb on error. Reset to prev state. */ msg->msg_iter = orig_iter; + skb->sk = sk; ___pskb_trim(skb, orig_len); + skb->sk = save_sk; return err; } -- 2.20.1