[PATCH v2 stable 6.1 1/2] tcp: fix races in tcp_abort()

[PATCH v2 stable 6.1 1/2] tcp: fix races in tcp_abort()

[Youngmin Nam]

From: Eric Dumazet <edumazet@google.com>

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().

We can use tcp_done_with_error() to centralize this logic.

Fixes: c1e64e298b8c ("net: diag: Support destroying TCP sockets.")
Signed-off-by: Eric Dumazet <edumazet@google.com>
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 | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 7d591a0cf0c7..1ad3a20eb9b7 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4755,13 +4755,9 @@ int tcp_abort(struct sock *sk, int err)
 	bh_lock_sock(sk);
 
 	if (!sock_flag(sk, SOCK_DEAD)) {
-		WRITE_ONCE(sk->sk_err, err);
-		/* This barrier is coupled with smp_rmb() in tcp_poll() */
-		smp_wmb();
-		sk_error_report(sk);
 		if (tcp_need_reset(sk->sk_state))
 			tcp_send_active_reset(sk, GFP_ATOMIC);
-		tcp_done(sk);
+		tcp_done_with_error(sk, err);
 	}
 
 	bh_unlock_sock(sk);
-- 
2.39.2

[PATCH v2 stable 6.1 2/2] tcp: fix forever orphan socket caused by tcp_abort

[Youngmin Nam]

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-email-lorenzo@google.com/
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 1ad3a20eb9b7..b64d53590f25 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4745,6 +4745,12 @@ 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);
@@ -4754,15 +4760,12 @@ 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;
 }
-- 
2.39.2

Re: [PATCH v2 stable 6.1 2/2] tcp: fix forever orphan socket caused by tcp_abort

[Sasha Levin]

[ 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: bac76cf89816bff06c4ec2f3df97dc34e150a1c4

WARNING: Author mismatch between patch and upstream commit:
Backport author: Youngmin Nam<youngmin.nam@samsung.com>
Commit author: Xueming Feng<kuro@kuroa.me>

Status in newer kernel trees:
6.13.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Present (different SHA1: ad383d4732d3)

Note: The patch differs from the upstream commit:
---
1:  bac76cf89816b ! 1:  f3878294629fd tcp: fix forever orphan socket caused by tcp_abort
    @@ Metadata
      ## Commit message ##
         tcp: fix forever orphan socket caused by tcp_abort
     
    +    commit bac76cf89816bff06c4ec2f3df97dc34e150a1c4 upstream.
    +
         We have some problem closing zero-window fin-wait-1 tcp sockets in our
         environment. This patch come from the investigation.
     
    @@ Commit message
         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 ##
     @@ net/ipv4/tcp.c: int tcp_abort(struct sock *sk, int err)
    - 		/* Don't race with userspace socket closes such as tcp_close. */
    - 		lock_sock(sk);
    + 	/* 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) {
    -+		if (!has_current_bpf_ctx())
    -+			release_sock(sk);
    ++		release_sock(sk);
     +		return -ENOENT;
     +	}
     +
    @@ net/ipv4/tcp.c: int tcp_abort(struct sock *sk, int err)
      
     -	if (!sock_flag(sk, SOCK_DEAD)) {
     -		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_with_error(sk, err);
     -	}
     +	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_with_error(sk, err);
      
      	bh_unlock_sock(sk);
      	local_bh_enable();
     -	tcp_write_queue_purge(sk);
    - 	if (!has_current_bpf_ctx())
    - 		release_sock(sk);
    + 	release_sock(sk);
      	return 0;
    + }
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.1.y        |  Success    |  Success   |

Re: [PATCH v2 stable 6.1 1/2] tcp: fix races in tcp_abort()

[Sasha Levin]

[ 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 Nam<youngmin.nam@samsung.com>
Commit author: Eric Dumazet<edumazet@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: 943f2b2b065a)

Note: The patch differs from the upstream commit:
---
1:  5ce4645c23cf5 ! 1:  0ff51ebdcc2ec 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-6.1.y        |  Success    |  Success   |