[Devel] [PATCH VZ9] drivers/vhost: fix missing rcu_read_lock in vhost_work_queue

[Pavel Tikhomirov]

In this stack:

  +-> vhost_vsock_dev_ioctl
    +-> vhost_vsock_start
      +-> vhost_work_queue
        +-> xas_find
          +-> xas_load
            +-> xas_start
              +-> xa_head
                +-> rcu_dereference_check

We require either rcu_read_lock or xa_lock but have none. Let's fix it
by calling a xa_find, which is a wraper for xas_find having proper rcu
and also xas_retry logic.

https://virtuozzo.atlassian.net/browse/PSBM-153264
Fixes: 5271bf51f1b83 ("ms/vhost: replace single worker pointer with xarray")
Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>

Feature: vhost-blk: in-kernel accelerator for virtio-blk guests
---
 drivers/vhost/vhost.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index c32557e279dfb..2f45c8d2b6fd6 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -257,10 +257,10 @@ static bool vhost_worker_queue(struct vhost_worker *worker,
 
 bool vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 {
-	XA_STATE(xas, &dev->worker_xa, 0);
 	struct vhost_worker *worker;
+	unsigned long i;
 
-	worker = xas_find(&xas, UINT_MAX);
+	worker = xa_find(&dev->worker_xa, &i, ULONG_MAX, XA_PRESENT);
 	if (!worker)
 		return false;
 
-- 
2.43.0