commit title seems truncated, can you check?
On Mon, Jul 27, 2026 at 03:13:02PM +0800, [email protected] wrote:
From: Nguyen Dinh Phi <[email protected]>
Syzbot report an issue which can be reproduced with these steps:
r0 = socket(AF_VSOCK, SOCK_STREAM, 0)
bind(r0, {VMADDR_CID_ANY, PORT})
connect(r0, {VMADDR_CID_LOCAL, PORT})
listen(r0, backlog)
r1 = socket(AF_VSOCK, SOCK_STREAM, 0)
connect(r1, {VMADDR_CID_LOCAL, PORT})
connect(r0 -> self) -> -1, EPROTO
listen(r0) -> 0
connect(r1 -> r0) -> 0
accept(r0) -> -1, EPROTO
I spent some time to understand this, what about changing in this way
(or something similar):
r0 = socket(AF_VSOCK, SOCK_STREAM, 0)
bind(r0, {VMADDR_CID_ANY, PORT})
connect(r0, {VMADDR_CID_LOCAL, PORT}) -> -1, EPROTO (self-connect)
listen(r0, backlog) -> 0
r1 = socket(AF_VSOCK, SOCK_STREAM, 0)
connect(r1, {VMADDR_CID_LOCAL, PORT}) -> 0
accept(r0) -> -1, EPROTO (stale sk_err)
Basically, it creates a socket (r0) and triggers a self-connect after
binding it. This self-connect fails with EPROTO because it loops back to
r0 while the socket is still in the TCP_SYN_SENT state, causing it to be
incorrectly dispatched to the connecting-client path. The unexpected
packet type encountered there sets sk_err to EPROTO.
After that, it invokes a listen() call on the same socket. This listen()
call succeeds because the kernel's listening path never inspects or
clears sk_err. Then, a new socket (r1) is created as a normal client and
connects to r0. However, vsock_accept() rejects this incoming connection
because the listener's sk_err still holds the EPROTO error from the
earlier failed self-connect.
This rejection causes the child socket created for r1's connection to
never be freed on virtio or hyperv transports; only the VMCI transport
implements pending_work to revisit and clean up a rejected socket
Fix the issue by using sock_error() to read the sk_err to prevent the
rejection branch from occurring in this scenario.
sock_error() atomically reads and clears sk_err, ensuring the error is
consumed when vsock_connect() returns and cannot affect subsequent
operations on the same socket. This matches the established pattern
used by other protocol connect() implementations in the network
stack like __inet_stream_connect(), tipc_wait_for_connect()...
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=1b2c9c4a0f8708082678
Fixes: d021c344051af ("VSOCK: Introduce VM Sockets")
Signed-off-by: Nguyen Dinh Phi <[email protected]>
---
V2: Add reproducer steps to commit message.
net/vmw_vsock/af_vsock.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 622dbd046799..43eddc33ed12 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1847,14 +1847,11 @@ static int vsock_connect(struct socket *sock, struct
sockaddr_unsized *addr,
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
}
- if (sk->sk_err) {
- err = -sk->sk_err;
+ err = sock_error(sk);
Should we do the same in other paths (e.g. send/recv) as well in a
follwup patch or in a series?
The patch itself LGTM.
Thanks,
Stefano
+ if (err) {
sk->sk_state = TCP_CLOSE;
sock->state = SS_UNCONNECTED;
- } else {
- err = 0;
}
-
out_wait:
finish_wait(sk_sleep(sk), &wait);
out:
--
2.53.0
