netdev - Re: Crash when receiving FIN-ACK in TCP_FIN

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Date:   Sun, 20 Oct 2019 17:15:49 -0600
From:   Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>
To:     Neal Cardwell <ncardwell@...gle.com>
Cc:     Netdev <netdev@...r.kernel.org>, Yuchung Cheng <ycheng@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: Crash when receiving FIN-ACK in TCP_FIN_WAIT1 state

> Hmm. Random related thought while searching for a possible cause: I
> wonder if tcp_write_queue_purge() should clear tp->highest_sack (and
> possibly tp->sacked_out)? The tcp_write_queue_purge() code is careful
> to call  tcp_clear_all_retrans_hints(tcp_sk(sk)) and I would imagine
> that similar considerations would imply that we should clear at least
> tp->highest_sack?
> 
> neal

Hi Neal

If the socket is in FIN-WAIT1, does that mean that all the segments
corresponding to SACK blocks are sent and ACKed already?

tp->sacked_out is non zero in all these crashes (is the SACK information
possibly invalid or stale here?).

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