netdev - Re: [RFC net] net: stream: don't purge sk_error

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Message-ID: <3b5549a2-cb0e-0dc1-3cb3-00d15a74873b@gmail.com>
Date:   Mon, 13 Sep 2021 22:14:00 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>, eric.dumazet@...il.com
Cc:     willemb@...gle.com, netdev@...r.kernel.org
Subject: Re: [RFC net] net: stream: don't purge sk_error_queue without holding
 its lock



On 9/13/21 3:38 PM, Jakub Kicinski wrote:
> sk_stream_kill_queues() can be called when there are still
> outstanding skbs to transmit. Those skbs may try to queue
> notifications to the error queue (e.g. timestamps).
> If sk_stream_kill_queues() purges the queue without taking
> its lock the queue may get corrupted.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
> Sending as an RFC for review, compile-tested only.
> 
> Seems far more likely that I'm missing something than that
> this has been broken forever and nobody noticed :S
> ---
>  net/core/stream.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/stream.c b/net/core/stream.c
> index 4f1d4aa5fb38..7c585088f394 100644
> --- a/net/core/stream.c
> +++ b/net/core/stream.c
> @@ -196,7 +196,7 @@ void sk_stream_kill_queues(struct sock *sk)
>  	__skb_queue_purge(&sk->sk_receive_queue);
>  
>  	/* Next, the error queue. */
> -	__skb_queue_purge(&sk->sk_error_queue);
> +	skb_queue_purge(&sk->sk_error_queue);
>  
>  	/* Next, the write queue. */
>  	WARN_ON(!skb_queue_empty(&sk->sk_write_queue));
> 


This should not be needed.

By definition, sk_stream_kill_queues() is only called when there is no
more references on the sockets.

So all outstanding packets must have been orphaned or freed.

Anyway, Linux-2.6.12-rc2 had no timestamps yet.