From: David Miller <davem@davemloft.net>
To: willemdebruijn.kernel@gmail.com
Cc: netdev@vger.kernel.org, edumazet@google.com, willemb@google.com
Subject: Re: [PATCH net] sock: correct sk_wmem_queued accounting on efault in tcp zerocopy
Date: Sun, 22 Oct 2017 01:52:00 +0100 (WEST) [thread overview]
Message-ID: <20171022.015200.2223977227108729125.davem@davemloft.net> (raw)
In-Reply-To: <20171019164039.20927-1-willemdebruijn.kernel@gmail.com>
From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: Thu, 19 Oct 2017 12:40:39 -0400
> From: Willem de Bruijn <willemb@google.com>
>
> 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 <willemb@google.com>
Applied.
prev parent reply other threads:[~2017-10-22 0:52 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-19 16:40 [PATCH net] sock: correct sk_wmem_queued accounting on efault in tcp zerocopy Willem de Bruijn
2017-10-19 16:45 ` Eric Dumazet
2017-10-22 0:52 ` David Miller [this message]
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