diff mbox series

[v1,net,12/15] af_unix: Use unix_recvq_full_lockless() in unix_stream_connect().

Message ID 20240603143231.62085-13-kuniyu@amazon.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series af_unix: Fix lockless access of sk->sk_state and others fields. | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 907 this patch: 907
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 5 of 5 maintainers
netdev/build_clang success Errors and warnings before: 905 this patch: 905
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 911 this patch: 911
netdev/checkpatch warning WARNING: line length of 86 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 1 now: 0
netdev/contest success net-next-2024-06-03--18-00 (tests: 1041)

Commit Message

Kuniyuki Iwashima June 3, 2024, 2:32 p.m. UTC 
Once sk->sk_state is changed to TCP_LISTEN, it never changes.

unix_accept() takes advantage of this characteristics; it does not
hold the listener's unix_state_lock() and only acquires recvq lock
to pop one skb.

It means unix_state_lock() does not prevent the queue length from
changing in unix_stream_connect().

Thus, we need to use unix_recvq_full_lockless() to avoid data-race.

Now we remove unix_recvq_full() as no one uses it.

Note that we can remove READ_ONCE() for sk->sk_max_ack_backlog in
unix_recvq_full_lockless() because of the following reasons:

  (1) For SOCK_DGRAM, it is a written-once field in unix_create1()

  (2) For SOCK_STREAM and SOCK_SEQPACKET, it is changed under the
      listener's unix_state_lock() in unix_listen(), and we hold
      the lock in unix_stream_connect()

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/unix/af_unix.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)
diff mbox series

Patch

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 6773f1465e50..88cda8af30d4 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -221,15 +221,9 @@  static inline int unix_may_send(struct sock *sk, struct sock *osk)
 	return unix_peer(osk) == NULL || unix_our_peer(sk, osk);
 }
 
-static inline int unix_recvq_full(const struct sock *sk)
-{
-	return skb_queue_len(&sk->sk_receive_queue) > sk->sk_max_ack_backlog;
-}
-
 static inline int unix_recvq_full_lockless(const struct sock *sk)
 {
-	return skb_queue_len_lockless(&sk->sk_receive_queue) >
-		READ_ONCE(sk->sk_max_ack_backlog);
+	return skb_queue_len_lockless(&sk->sk_receive_queue) > sk->sk_max_ack_backlog;
 }
 
 struct sock *unix_peer_get(struct sock *s)
@@ -1545,7 +1539,7 @@  static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	if (other->sk_shutdown & RCV_SHUTDOWN)
 		goto out_unlock;
 
-	if (unix_recvq_full(other)) {
+	if (unix_recvq_full_lockless(other)) {
 		err = -EAGAIN;
 		if (!timeo)
 			goto out_unlock;