Re: [PATCH v3 2/2] vsock/virtio: avoid refilling the RX queue after teardown

[Bobby Eshleman <bobbyeshleman@gmail.com>]

On Wed, Jul 29, 2026 at 12:16:55PM -0700, Weiming Shi wrote:
> Commit b917507e5ad9 ("vsock/virtio: stop workers during the .remove()")
> made the RX worker jump to its common exit when rx_run is clear.  That
> exit still refills the RX queue when the buffer count is low, so work
> queued across virtio_vsock_vqs_del() can add buffers after the virtqueues
> have been deleted.
> 
> BUG: KASAN: slab-use-after-free in virtqueue_add_sgs
> Read of size 4 by task kworker/0:1
> Workqueue: virtio_vsock virtio_transport_rx_work
> Call Trace:
>  virtqueue_add_sgs (drivers/virtio/virtio_ring.c:2796)
>  virtio_vsock_rx_fill (net/vmw_vsock/virtio_transport.c:332)
>  virtio_transport_rx_work (net/vmw_vsock/virtio_transport.c:701)
>  process_one_work (kernel/workqueue.c:3314)
>  worker_thread (kernel/workqueue.c:3478)
>  kthread (kernel/kthread.c:436)
>  ret_from_fork (arch/x86/kernel/process.c:158)
>  ret_from_fork_asm (arch/x86/entry/entry_64.S:245)
> ...
> Freed by task 141:
>  kfree (mm/slub.c:6566)
>  vp_del_vq (drivers/virtio/virtio_pci_common.c:259)
>  vp_del_vqs (drivers/virtio/virtio_pci_common.c:285)
>  virtio_vsock_freeze (net/vmw_vsock/virtio_transport.c:912)
>  virtio_device_freeze (drivers/virtio/virtio.c:658)
>  virtio_pci_freeze (drivers/virtio/virtio_pci_common.c:601)
>  pci_pm_freeze (drivers/pci/pci-driver.c:1098)
>  device_suspend (drivers/base/power/main.c:1968)
> Kernel panic - not syncing: KASAN: panic_on_warn set ...
> 
> Jump to a no-refill exit when rx_run is clear, leaving the normal exit
> to replenish a running queue.
> 
> Fixes: b917507e5ad9 ("vsock/virtio: stop workers during the .remove()")
> Cc: stable@vger.kernel.org
> Reported-by: Xiang Mei <xmei5@asu.edu>
> Link: https://lore.kernel.org/r/20260727035804.1860862-1-bestswngs@gmail.com
> Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
> Assisted-by: OpenAI-Codex:gpt-5
> Signed-off-by: Weiming Shi <bestswngs@gmail.com>
> ---
>  net/vmw_vsock/virtio_transport.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
> index a8e1dd95ba8c..96c9fe8d357c 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -638,7 +638,7 @@ static void virtio_transport_rx_work(struct work_struct *work)
>  	mutex_lock(&vsock->rx_lock);
>  
>  	if (!vsock->rx_run)
> -		goto out;
> +		goto out_nofill;
>  
>  	vq = vsock->vqs[VSOCK_VQ_RX];
>  
> @@ -692,6 +692,7 @@ static void virtio_transport_rx_work(struct work_struct *work)
>  out:
>  	if (vsock->rx_buf_nr < vsock->rx_buf_max_nr / 2)
>  		virtio_vsock_rx_fill(vsock);
> +out_nofill:
>  	mutex_unlock(&vsock->rx_lock);
>  }
>  
> -- 
> 2.55.0
> 

Reviewed-by: Bobby Eshleman <bobbyeshleman@meta.com>