[Devel] [PATCH RHEL9 COMMIT] drivers/vhost: fix missing rcu_read_lock in vhost_work_queue

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-362.8.1.vz9.35.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh9-5.14.0-362.8.1.vz9.35.7
------>
commit 17ad03ac78b94dc1fcdf3a76758a43b4efc439ee
Author: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
Date:   Mon Jan 22 14:54:21 2024 +0800

    drivers/vhost: fix missing rcu_read_lock in vhost_work_queue
    
    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 c32557e279df..2f45c8d2b6fd 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;