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vsock: avoid timeout during connect() if the socket is closing 

When a peer attempts to establish a connection, vsock_connect() contains
a loop that waits for the state to be TCP_ESTABLISHED. However, the
other peer can be fast enough to accept the connection and close it
immediately, thus moving the state to TCP_CLOSING.

When this happens, the peer in the vsock_connect() is properly woken up,
but since the state is not TCP_ESTABLISHED, it goes back to sleep
until the timeout expires, returning -ETIMEDOUT.

If the socket state is TCP_CLOSING, waiting for the timeout is pointless.
vsock_connect() can return immediately without errors or delay since the
connection actually happened. The socket will be in a closing state,
but this is not an issue, and subsequent calls will fail as expected.

We discovered this issue while developing a test that accepts and
immediately closes connections to stress the transport switch between
two connect() calls, where the first one was interrupted by a signal
(see Closes link).

Reported-by: Luigi Leonardi <leonardi@redhat.com>
Closes: https://lore.kernel.org/virtualization/bq6hxrolno2vmtqwcvb5bljfpb7mvwb3kohrvaed6auz5vxrfv@ijmd2f3grobn/
Fixes: d021c34405 ("VSOCK: Introduce VM Sockets")
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Tested-by: Luigi Leonardi <leonardi@redhat.com>
Reviewed-by: Luigi Leonardi <leonardi@redhat.com>
Link: https://patch.msgid.link/20250328141528.420719-1-sgarzare@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Stefano Garzarella 2025-03-28 15:15:28 +01:00 committed by Jakub Kicinski
parent 0ff0faf7af
commit fccd2b711d
1 changed files with 5 additions and 1 deletions
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6
net/vmw_vsock/af_vsock.c
View File

@ -1551,7 +1551,11 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
timeout = vsk->connect_timeout;
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
while (sk->sk_state != TCP_ESTABLISHED && sk->sk_err == 0) {
/* If the socket is already closing or it is in an error state, there
* is no point in waiting.
*/
while (sk->sk_state != TCP_ESTABLISHED &&
sk->sk_state != TCP_CLOSING && sk->sk_err == 0) {
if (flags & O_NONBLOCK) {
/* If we're not going to block, we schedule a timeout
* function to generate a timeout on the connection