[PATCH 5.13 112/151] vsock/virtio: avoid potential deadlock when vsock device remove

Greg Kroah-Hartman
2021-08-16T13:29:45Z

From: Longpeng(Mike) <longpeng2@huawei.com>

[ Upstream commit 49b0b6ffe20c5344f4173f3436298782a08da4f2 ]

There's a potential deadlock case when remove the vsock device or
process the RESET event:

vsock_for_each_connected_socket:
spin_lock_bh(&vsock_table_lock) ----------- (1)
...
virtio_vsock_reset_sock:
lock_sock(sk) --------------------- (2)
...
spin_unlock_bh(&vsock_table_lock)

lock_sock() may do initiative schedule when the 'sk' is owned by
other thread at the same time, we would receivce a warning message
that "scheduling while atomic".

Even worse, if the next task (selected by the scheduler) try to
release a 'sk', it need to request vsock_table_lock and the deadlock
occur, cause the system into softlockup state.
Call trace:
queued_spin_lock_slowpath
vsock_remove_bound
vsock_remove_sock
virtio_transport_release
__vsock_release
vsock_release
__sock_release
sock_close
__fput
____fput

So we should not require sk_lock in this case, just like the behavior
in vhost_vsock or vmci.

Fixes: 0ea9e1d3a9e3 ("VSOCK: Introduce virtio_transport.ko")
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20210812053056.1699-1-longpeng2@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/vmw_vsock/virtio_transport.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index 2700a63ab095..3a056f8affd1 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -356,11 +356,14 @@ static void virtio_vsock_event_fill(struct virtio_vsock *vsock)

static void virtio_vsock_reset_sock(struct sock *sk)
{
- lock_sock(sk);
+ /* vmci_transport.c doesn't take sk_lock here either. At least we're
+ * under vsock_table_lock so the sock cannot disappear while we're
+ * executing.
+ */
+
sk->sk_state = TCP_CLOSE;
sk->sk_err = ECONNRESET;
sk->sk_error_report(sk);
- release_sock(sk);
}

static void virtio_vsock_update_guest_cid(struct virtio_vsock *vsock)
--
2.30.2