On Mon, Jul 20, 2026 at 01:22:40PM +0300, Andrey Drobyshev wrote:
vhost_vq_work_queue() only holds the RCU read lock while it dereferences vq->worker and queues work on it. vhost_workers_free() however clears the vq->worker pointers and immediately frees the workers, without waiting for a grace period. A caller that fetched the worker right before the pointer was cleared can therefore still be queueing work on it while it is freed. And even when the queueing itself wins the race, the work is never run, so its VHOST_WORK_QUEUED bit stays set and all future attempts to queue it are silently skipped.None of the current callers can actually hit this: net and scsi stop their virtqueues before the workers are freed, and vsock unhashes the device and does synchronize_rcu() of its own in vhost_vsock_dev_release() before the workers go away. But the upcoming VHOST_RESET_OWNER support in vhost-vsock keeps the device hashed while its workers are freed, so the lockless send/cancel paths become able to race with the teardown. Fix this by clearing the vq->worker pointers, waiting for a grace period, and then flushing the workers so any work the last readers queued runs before the workers are freed. Fixes: 228a27cf78af ("vhost: Allow worker switching while work is queueing") Suggested-by: Stefano Garzarella <[email protected]> Signed-off-by: Andrey Drobyshev <[email protected]> --- drivers/vhost/vhost.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
Reviewed-by: Stefano Garzarella <[email protected]>
