From: Jerome Mohm <[email protected]>
vsock_bpf_recvmsg() takes lock_sock(sk) and holds it across the whole
receive loop, including vsock_msg_wait_data(), which sleeps in
wait_woken() without dropping the lock. When data arrives, the
transport's delivery context (the vsock-loopback worker, or the
virtio/vhost rx path) calls virtio_transport_recv_pkt() -> lock_sock()
on the same socket and blocks. That context is the only one that would
queue the skb and call sk_data_ready() to wake the reader, so neither
side makes progress. A blocking recv() hangs until a signal arrives (a
finite SO_RCVTIMEO also breaks it); while it lasts the shared delivery
worker is stalled, so all vsock rx on that transport stops, not only
the affected socket. The hung-task watchdog reports the worker blocked
in D state:
INFO: task kworker/1:3:107 blocked for more than 5 seconds.
task:kworker/1:3 state:D Workqueue: vsock-loopback vsock_loopback_work
Call Trace:
__schedule
schedule
__lock_sock
lock_sock_nested
virtio_transport_recv_pkt
vsock_loopback_work
The reader holds the same sk_lock-AF_VSOCK it is waiting on, taken in
vsock_bpf_recvmsg().
This code is based on net/unix/unix_bpf.c, whose unix_msg_wait_data()
drops u->iolock around wait_woken() and re-takes it afterwards. The
vsock port substituted lock_sock() for that serialisation lock but
omitted the unlock and relock. tcp_bpf and the native
vsock_connectible_wait_data() both drop the lock across the wait;
vsock_bpf is the only one that does not.
Release the socket lock around the wait and re-acquire it before
re-checking for data, so the caller's locking is unchanged.
Fixes: 634f1a7110b4 ("vsock: support sockmap")
Cc: [email protected]
Assisted-by: LLM
Signed-off-by: Jerome Mohm <[email protected]>
---
net/vmw_vsock/vsock_bpf.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c
index 9049d2648646..bb7d81a95baa 100644
--- a/net/vmw_vsock/vsock_bpf.c
+++ b/net/vmw_vsock/vsock_bpf.c
@@ -50,7 +50,9 @@ static bool vsock_msg_wait_data(struct sock *sk, struct
sk_psock *psock, long ti
sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
ret = vsock_has_data(sk, psock);
if (!ret) {
+ release_sock(sk);
wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
+ lock_sock(sk);
ret = vsock_has_data(sk, psock);
}
sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
---
base-commit: 72d3fcf802c45d00b300f25b848a93c3a2bd7c7e
change-id: 20260929-kbh3-1-022-fix-340aa3f7f071
Best regards,
--
Jerome Mohm <[email protected]>
