Re: [PATCH 2/2] tcp: fix forever orphan socket caused by tcp_abort

[Greg KH]

On Fri, Mar 14, 2025 at 06:24:46PM +0900, Youngmin Nam wrote:
> From: Xueming Feng <kuro@xxxxxxxx>
> 
> commit bac76cf89816bff06c4ec2f3df97dc34e150a1c4 upstream.
> 
> We have some problem closing zero-window fin-wait-1 tcp sockets in our
> environment. This patch come from the investigation.
> 
> Previously tcp_abort only sends out reset and calls tcp_done when the
> socket is not SOCK_DEAD, aka orphan. For orphan socket, it will only
> purging the write queue, but not close the socket and left it to the
> timer.
> 
> While purging the write queue, tp->packets_out and sk->sk_write_queue
> is cleared along the way. However tcp_retransmit_timer have early
> return based on !tp->packets_out and tcp_probe_timer have early
> return based on !sk->sk_write_queue.
> 
> This caused ICSK_TIME_RETRANS and ICSK_TIME_PROBE0 not being resched
> and socket not being killed by the timers, converting a zero-windowed
> orphan into a forever orphan.
> 
> This patch removes the SOCK_DEAD check in tcp_abort, making it send
> reset to peer and close the socket accordingly. Preventing the
> timer-less orphan from happening.
> 
> According to Lorenzo's email in the v1 thread, the check was there to
> prevent force-closing the same socket twice. That situation is handled
> by testing for TCP_CLOSE inside lock, and returning -ENOENT if it is
> already closed.
> 
> The -ENOENT code comes from the associate patch Lorenzo made for
> iproute2-ss; link attached below, which also conform to RFC 9293.
> 
> At the end of the patch, tcp_write_queue_purge(sk) is removed because it
> was already called in tcp_done_with_error().
> 
> p.s. This is the same patch with v2. Resent due to mis-labeled "changes
> requested" on patchwork.kernel.org.
> 
> Link: https://patchwork.ozlabs.org/project/netdev/patch/1450773094-7978-3-git-send-email-lorenzo@xxxxxxxxxx/
> Fixes: c1e64e298b8c ("net: diag: Support destroying TCP sockets.")
> Signed-off-by: Xueming Feng <kuro@xxxxxxxx>
> Tested-by: Lorenzo Colitti <lorenzo@xxxxxxxxxx>
> Reviewed-by: Jason Xing <kerneljasonxing@xxxxxxxxx>
> Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Link: https://patch.msgid.link/20240826102327.1461482-1-kuro@xxxxxxxx
> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # v5.10+

Does not apply to 6.1.y or older, what did you want this applied to?

thanks,

greg k-h