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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: Hannes Frederic Sowa , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Jann Horn X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1778871255; l=1598; i=jannh@google.com; s=20240730; h=from:subject:message-id; bh=DB0n+V52Tzs8cERe6V5xZXHKeaQoXCM9NaKvtCnxM7M=; b=h9yWkuv++lnVf+DshyCBAH42pN5rw+SC/SRama1UcOBNv1YYgQEbZsgSV6YnzcnjwKb3Bz+g5 W+jyAq2FhLJA2jwhLG2iPh8SGK3nRNWwM4DtTg9FVTirTkeIOSMGYN9 X-Developer-Key: i=jannh@google.com; a=ed25519; pk=AljNtGOzXeF6khBXDJVVvwSEkVDGnnZZYqfWhP1V+C8= Currently, a blocking recv() on a unix stream socket will wake up every time an SKB that was sent from the socket is consumed by the peer. So, in a synchronous communication scenario where the client sends a message to the server, and then the client blocks in recv() until it receives a reply from the server, the client will get a spurious wakeup when the server receives the client's message. Similar to other receive paths such as __skb_wait_for_more_packets(), use DEFINE_WAIT_FUNC() to filter wakeups. Signed-off-by: Jann Horn --- net/unix/af_unix.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index b38804e2c5ac..f36ab3e5a5bb 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2707,6 +2707,14 @@ static int unix_read_skb(struct sock *sk, skb_read_actor_t recv_actor) return recv_actor(sk, skb); } +static int unix_recv_wake(wait_queue_entry_t *wait, unsigned int mode, + int sync, void *key) +{ + if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR))) + return 0; + return autoremove_wake_function(wait, mode, sync, key); +} + /* * Sleep until more data has arrived. But check for races.. */ @@ -2715,7 +2723,7 @@ __releases(&unix_sk(sk)->iolock) __releases(&unix_sk(sk)->lock) { unsigned int state = TASK_INTERRUPTIBLE | freezable * TASK_FREEZABLE; - DEFINE_WAIT(wait); + DEFINE_WAIT_FUNC(wait, unix_recv_wake); prepare_to_wait(sk_sleep(sk), &wait, state); unix_state_unlock(sk); -- 2.54.0.563.g4f69b47b94-goog