diff mbox series

[mptcp-net,4/4] mptcp: add annotations around sk->sk_shutdown accesses

Message ID 4ea2e7aeea3fdfdaeaca9aa431ca66df205f68fb.1684321532.git.pabeni@redhat.com (mailing list archive)
State Superseded, archived
Delegated to: Paolo Abeni
Headers show
Series mptcp: a bunch of data race fixes | expand

Checks

Context Check Description
matttbe/checkpatch success total: 0 errors, 0 warnings, 0 checks, 83 lines checked
matttbe/build warning Build error with: make C=1 net/mptcp/protocol.o
matttbe/KVM_Validation__normal__except_selftest_mptcp_join_ success Success! ✅
matttbe/KVM_Validation__normal__only_selftest_mptcp_join_ success Success! ✅
matttbe/KVM_Validation__debug__only_selftest_mptcp_join_ success Success! ✅
matttbe/KVM_Validation__debug__except_selftest_mptcp_join_ warning Unstable: 3 failed test(s): packetdrill_add_addr packetdrill_fastopen selftest_diag

Commit Message

Paolo Abeni May 17, 2023, 11:35 a.m. UTC 
Christoph reported the mptcp variant of a recently addressed plain
TCP issue. Similar to commit e14cadfd80d7 ("tcp: add annotations around
sk->sk_shutdown accesses") add READ/WRITE ONCE annotations to silence
KCSAN reports around lockless sk_shutdown access.

Fixes: 71ba088ce0aa ("mptcp: cleanup accept and poll")
Reported-by: Christoph Paasch <cpaasch@apple.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/401
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/mptcp/protocol.c | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

Comments

MPTCP CI May 17, 2023, 12:05 p.m. UTC | #1 
Hi Paolo,

Thank you for your modifications, that's great!

But sadly, our CI spotted some issues with it when trying to build it.

You can find more details there:

  https://patchwork.kernel.org/project/mptcp/patch/4ea2e7aeea3fdfdaeaca9aa431ca66df205f68fb.1684321532.git.pabeni@redhat.com/
  https://github.com/multipath-tcp/mptcp_net-next/actions/runs/5002837724

Status: failure
Initiator: MPTCPimporter
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/4d1ad0619b22

Feel free to reply to this email if you cannot access logs, if you need
some support to fix the error, if this doesn't seem to be caused by your
modifications or if the error is a false positive one.

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (Tessares)
MPTCP CI May 17, 2023, 1:10 p.m. UTC | #2 
Hi Paolo,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal (except selftest_mptcp_join):
  - Success! ✅:
  - Task: https://cirrus-ci.com/task/5312510186749952
  - Summary: https://api.cirrus-ci.com/v1/artifact/task/5312510186749952/summary/summary.txt

- KVM Validation: normal (only selftest_mptcp_join):
  - Success! ✅:
  - Task: https://cirrus-ci.com/task/6438410093592576
  - Summary: https://api.cirrus-ci.com/v1/artifact/task/6438410093592576/summary/summary.txt

- KVM Validation: debug (only selftest_mptcp_join):
  - Success! ✅:
  - Task: https://cirrus-ci.com/task/6156935116881920
  - Summary: https://api.cirrus-ci.com/v1/artifact/task/6156935116881920/summary/summary.txt

- KVM Validation: debug (except selftest_mptcp_join):
  - Unstable: 3 failed test(s): packetdrill_add_addr packetdrill_fastopen selftest_diag
diff mbox series

Patch

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 379ae468d755..21c19a0e0dfb 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -603,7 +603,7 @@  static bool mptcp_check_data_fin(struct sock *sk)
 		WRITE_ONCE(msk->ack_seq, msk->ack_seq + 1);
 		WRITE_ONCE(msk->rcv_data_fin, 0);
 
-		sk->sk_shutdown |= RCV_SHUTDOWN;
+		WRITE_ONCE(sk->sk_shutdown, sk->sk_shutdown | RCV_SHUTDOWN);
 		smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
 
 		switch (sk->sk_state) {
@@ -910,7 +910,7 @@  static void mptcp_check_for_eof(struct mptcp_sock *msk)
 		/* hopefully temporary hack: propagate shutdown status
 		 * to msk, when all subflows agree on it
 		 */
-		sk->sk_shutdown |= RCV_SHUTDOWN;
+		WRITE_ONCE(sk->sk_shutdown, sk->sk_shutdown | RCV_SHUTDOWN);
 
 		smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
 		sk->sk_data_ready(sk);
@@ -2553,7 +2553,7 @@  static void mptcp_check_fastclose(struct mptcp_sock *msk)
 	}
 
 	inet_sk_state_store(sk, TCP_CLOSE);
-	sk->sk_shutdown = SHUTDOWN_MASK;
+	WRITE_ONCE(sk->sk_shutdown, SHUTDOWN_MASK);
 	smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
 	set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags);
 
@@ -3006,7 +3006,7 @@  bool __mptcp_close(struct sock *sk, long timeout)
 	bool do_cancel_work = false;
 	int subflows_alive = 0;
 
-	sk->sk_shutdown = SHUTDOWN_MASK;
+	WRITE_ONCE(sk->sk_shutdown, SHUTDOWN_MASK);
 
 	if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE)) {
 		mptcp_listen_inuse_dec(sk);
@@ -3149,7 +3149,7 @@  static int mptcp_disconnect(struct sock *sk, int flags)
 	mptcp_pm_data_reset(msk);
 	mptcp_ca_reset(sk);
 
-	sk->sk_shutdown = 0;
+	WRITE_ONCE(sk->sk_shutdown, 0);
 	sk_error_report(sk);
 	return 0;
 }
@@ -3856,9 +3856,6 @@  static __poll_t mptcp_check_writeable(struct mptcp_sock *msk)
 {
 	struct sock *sk = (struct sock *)msk;
 
-	if (unlikely(sk->sk_shutdown & SEND_SHUTDOWN))
-		return EPOLLOUT | EPOLLWRNORM;
-
 	if (sk_stream_is_writeable(sk))
 		return EPOLLOUT | EPOLLWRNORM;
 
@@ -3876,6 +3873,7 @@  static __poll_t mptcp_poll(struct file *file, struct socket *sock,
 	struct sock *sk = sock->sk;
 	struct mptcp_sock *msk;
 	__poll_t mask = 0;
+	u8 shutdown;
 	int state;
 
 	msk = mptcp_sk(sk);
@@ -3892,17 +3890,22 @@  static __poll_t mptcp_poll(struct file *file, struct socket *sock,
 		return inet_csk_listen_poll(ssock->sk);
 	}
 
+	shutdown = READ_ONCE(sk->sk_shutdown);
+	if (shutdown == SHUTDOWN_MASK || state == TCP_CLOSE)
+		mask |= EPOLLHUP;
+	if (shutdown & RCV_SHUTDOWN)
+		mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;
+
 	if (state != TCP_SYN_SENT && state != TCP_SYN_RECV) {
 		mask |= mptcp_check_readable(msk);
-		mask |= mptcp_check_writeable(msk);
+		if (shutdown & SEND_SHUTDOWN)
+			mask |= EPOLLOUT | EPOLLWRNORM;
+		else
+			mask |= mptcp_check_writeable(msk);
 	} else if (state == TCP_SYN_SENT && inet_sk(sk)->defer_connect) {
 		/* cf tcp_poll() note about TFO */
 		mask |= EPOLLOUT | EPOLLWRNORM;
 	}
-	if (sk->sk_shutdown == SHUTDOWN_MASK || state == TCP_CLOSE)
-		mask |= EPOLLHUP;
-	if (sk->sk_shutdown & RCV_SHUTDOWN)
-		mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;
 
 	/* This barrier is coupled with smp_wmb() in __mptcp_error_report() */
 	smp_rmb();