Commit 0762262ac3e7 for kernel

commit 0762262ac3e70f65b3bb843fe892f8bac1562d08
Author: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Date:   Thu May 7 15:43:15 2026 +0000

    mshv: Fix race in mshv_irqfd_deassign

    mshv_irqfd_deactivate() and the hlist traversal of pt_irqfds_list
    require pt->pt_irqfds_lock to be held, but mshv_irqfd_deassign()
    omits it. This races with the EPOLLHUP path in mshv_irqfd_wakeup(),
    which does take the lock before calling mshv_irqfd_deactivate().

    Additionally, mshv_irqfd_deactivate() uses hlist_del() which poisons
    the node pointers rather than resetting them. Since
    mshv_irqfd_is_active() relies on hlist_unhashed() (checks pprev ==
    NULL), a poisoned node still appears active. If a concurrent path calls
    mshv_irqfd_deactivate() again on the same irqfd, the guard fails to
    prevent a double hlist_del() on poisoned pointers.

    Fix both issues:
    - Add the missing spin_lock_irq/spin_unlock_irq around the list
      traversal in mshv_irqfd_deassign(), matching mshv_irqfd_release().
    - Use hlist_del_init() instead of hlist_del() so the node is properly
      marked as unhashed after removal, making the is_active guard reliable.

    Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
    Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
    Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
    Signed-off-by: Wei Liu <wei.liu@kernel.org>

diff --git a/drivers/hv/mshv_eventfd.c b/drivers/hv/mshv_eventfd.c
index 90959f639dc3..5995a62aff8d 100644
--- a/drivers/hv/mshv_eventfd.c
+++ b/drivers/hv/mshv_eventfd.c
@@ -284,7 +284,7 @@ static void mshv_irqfd_deactivate(struct mshv_irqfd *irqfd)
 	if (!mshv_irqfd_is_active(irqfd))
 		return;

-	hlist_del(&irqfd->irqfd_hnode);
+	hlist_del_init(&irqfd->irqfd_hnode);

 	queue_work(irqfd_cleanup_wq, &irqfd->irqfd_shutdown);
 }
@@ -541,13 +541,14 @@ static int mshv_irqfd_deassign(struct mshv_partition *pt,
 	if (IS_ERR(eventfd))
 		return PTR_ERR(eventfd);

+	spin_lock_irq(&pt->pt_irqfds_lock);
 	hlist_for_each_entry_safe(irqfd, n, &pt->pt_irqfds_list,
 				  irqfd_hnode) {
 		if (irqfd->irqfd_eventfd_ctx == eventfd &&
 		    irqfd->irqfd_irqnum == args->gsi)
-
 			mshv_irqfd_deactivate(irqfd);
 	}
+	spin_unlock_irq(&pt->pt_irqfds_lock);

 	eventfd_ctx_put(eventfd);