Re: [PATCH] net/vmw_vsock: improve locking in vsock_connect_timeout()
From: Stefano Garzarella <sgarzare@redhat.com>
Date: 2021-02-05 17:25:11
On Fri, Feb 05, 2021 at 03:32:02PM +0100, Norbert Slusarek wrote:
From: Norbert Slusarek <redacted>
Date: Fri, 5 Feb 2021 13:14:05 +0100
Subject: [PATCH] net/vmw_vsock: improve locking in vsock_connect_timeout()
A possible locking issue in vsock_connect_timeout() was recognized by
Eric Dumazet which might cause a null pointer dereference in
vsock_transport_cancel_pkt(). This patch assures that
vsock_transport_cancel_pkt() will be called within the lock, so a race
condition won't occur which could result in vsk->transport to be set to NULL.
Fixes: 380feae0def7 ("vsock: cancel packets when failing to connect")
I have a doubt about the tag to use, since until we introduced
transports in commit c0cfa2d8a788 ("vsock: add multi-transports
support") this issue didn't cause many problems.
But it must be said that in the commit 380feae0def7 ("vsock: cancel
packets when failing to connect") the vsock_transport_cancel_pkt() was
called with the lock held in vsock_stream_connect() and without lock in
vsock_connect_timeout(), so maybe this tag is okay.
Anyway, the patch LGTM:
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
quoted hunk ↗ jump to hunk
Reported-by: Eric Dumazet <redacted> Signed-off-by: Norbert Slusarek <redacted> --- net/vmw_vsock/af_vsock.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index 6894f21dc147..ad7dd9d93b5b 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c@@ -1243,7 +1243,6 @@ static void vsock_connect_timeout(struct work_struct *work){ struct sock *sk; struct vsock_sock *vsk; - int cancel = 0; vsk = container_of(work, struct vsock_sock, connect_work.work); sk = sk_vsock(vsk);@@ -1254,11 +1253,9 @@ static void vsock_connect_timeout(struct work_struct *work)sk->sk_state = TCP_CLOSE; sk->sk_err = ETIMEDOUT; sk->sk_error_report(sk); - cancel = 1; + vsock_transport_cancel_pkt(vsk); } release_sock(sk); - if (cancel) - vsock_transport_cancel_pkt(vsk); sock_put(sk); } -- 2.30.0