From: Xueming Feng kuro@kuroa.me

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... Fixes: c1e64e298b8c ("net: diag: Support destroying TCP sockets.") Signed-off-by: Xueming Feng kuro@kuroa.me Tested-by: Lorenzo Colitti lorenzo@google.com Reviewed-by: Jason Xing kerneljasonxing@gmail.com Reviewed-by: Eric Dumazet edumazet@google.com Link: https://patch.msgid.link/20240826102327.1461482-1-kuro@kuroa.me Signed-off-by: Jakub Kicinski kuba@kernel.org Cc: stable@vger.kernel.org Link: https://lore.kernel.org/lkml/Z9OZS%2Fhc+v5og6%2FU@perf/ [youngmin: Resolved minor conflict in net/ipv4/tcp.c] Signed-off-by: Youngmin Nam youngmin.nam@samsung.com --- net/ipv4/tcp.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index c1e624ca6a25..7ff0ecb59579 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -4504,6 +4504,12 @@ int tcp_abort(struct sock *sk, int err) /* Don't race with userspace socket closes such as tcp_close. */ lock_sock(sk);

+ /* Avoid closing the same socket twice. */ + if (sk->sk_state == TCP_CLOSE) { + release_sock(sk); + return -ENOENT; + } + if (sk->sk_state == TCP_LISTEN) { tcp_set_state(sk, TCP_CLOSE); inet_csk_listen_stop(sk); @@ -4513,15 +4519,12 @@ int tcp_abort(struct sock *sk, int err) local_bh_disable(); bh_lock_sock(sk);

- if (!sock_flag(sk, SOCK_DEAD)) { - if (tcp_need_reset(sk->sk_state)) - tcp_send_active_reset(sk, GFP_ATOMIC); - tcp_done_with_error(sk, err); - } + if (tcp_need_reset(sk->sk_state)) + tcp_send_active_reset(sk, GFP_ATOMIC); + tcp_done_with_error(sk, err);

bh_unlock_sock(sk); local_bh_enable(); - tcp_write_queue_purge(sk); release_sock(sk); return 0; }

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected. No action required from the submitter.

The upstream commit SHA1 provided is correct: 5ce4645c23cf5f048eb8e9ce49e514bababdee85

WARNING: Author mismatch between patch and upstream commit: Backport author: Youngmin Namyoungmin.nam@samsung.com Commit author: Eric Dumazetedumazet@google.com

Status in newer kernel trees: 6.13.y | Present (exact SHA1) 6.12.y | Present (exact SHA1) 6.6.y | Present (different SHA1: aa5229129a55) 6.1.y | Present (different SHA1: a1146efaea31)

Note: The patch differs from the upstream commit: --- 1: 5ce4645c23cf5 ! 1: 2295e520401c3 tcp: fix races in tcp_abort() @@ Commit message tcp_abort() has the same issue than the one fixed in the prior patch in tcp_write_err().

+ commit 5ce4645c23cf5f048eb8e9ce49e514bababdee85 upstream. + + To apply commit bac76cf89816bff06c4ec2f3df97dc34e150a1c4, + this patch must be applied first. + In order to get consistent results from tcp_poll(), we must call sk_error_report() after tcp_done().

@@ Commit message Acked-by: Neal Cardwell ncardwell@google.com Link: https://lore.kernel.org/r/20240528125253.1966136-4-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org + Cc: stable@vger.kernel.org + [youngmin: Resolved minor conflict in net/ipv4/tcp.c] + Signed-off-by: Youngmin Nam youngmin.nam@samsung.com

## net/ipv4/tcp.c ## @@ net/ipv4/tcp.c: int tcp_abort(struct sock *sk, int err) @@ net/ipv4/tcp.c: int tcp_abort(struct sock *sk, int err) - smp_wmb(); - sk_error_report(sk); if (tcp_need_reset(sk->sk_state)) - tcp_send_active_reset(sk, GFP_ATOMIC, - SK_RST_REASON_NOT_SPECIFIED); + tcp_send_active_reset(sk, GFP_ATOMIC); - tcp_done(sk); + tcp_done_with_error(sk, err); } ---

Results of testing on various branches:

| Branch | Patch Apply | Build Test | |---------------------------|-------------|------------| | stable/linux-5.15.y | Success | Success |