Patch "vhost-scsi: Handle vhost_vq_work_queue failures for events" has been added to the 6.6-stable tree

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This is a note to let you know that I've just added the patch titled

    vhost-scsi: Handle vhost_vq_work_queue failures for events

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     vhost-scsi-handle-vhost_vq_work_queue-failures-for-e.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 1d0818641b42a014368264ef3886668e52b38bdf
Author: Mike Christie <michael.christie@xxxxxxxxxx>
Date:   Fri Mar 15 19:46:59 2024 -0500

    vhost-scsi: Handle vhost_vq_work_queue failures for events
    
    [ Upstream commit b1b2ce58ed23c5d56e0ab299a5271ac01f95b75c ]
    
    Currently, we can try to queue an event's work before the vhost_task is
    created. When this happens we just drop it in vhost_scsi_do_plug before
    even calling vhost_vq_work_queue. During a device shutdown we do the
    same thing after vhost_scsi_clear_endpoint has cleared the backends.
    
    In the next patches we will be able to kill the vhost_task before we
    have cleared the endpoint. In that case, vhost_vq_work_queue can fail
    and we will leak the event's memory. This has handle the failure by
    just freeing the event. This is safe to do, because
    vhost_vq_work_queue will only return failure for us when the vhost_task
    is killed and so userspace will not be able to handle events if we
    sent them.
    
    Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
    Message-Id: <20240316004707.45557-2-michael.christie@xxxxxxxxxx>
    Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index abef0619c7901..8f17d29ab7e9c 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -497,10 +497,8 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
 		vq_err(vq, "Faulted on vhost_scsi_send_event\n");
 }
 
-static void vhost_scsi_evt_work(struct vhost_work *work)
+static void vhost_scsi_complete_events(struct vhost_scsi *vs, bool drop)
 {
-	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
-					vs_event_work);
 	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
 	struct vhost_scsi_evt *evt, *t;
 	struct llist_node *llnode;
@@ -508,12 +506,20 @@ static void vhost_scsi_evt_work(struct vhost_work *work)
 	mutex_lock(&vq->mutex);
 	llnode = llist_del_all(&vs->vs_event_list);
 	llist_for_each_entry_safe(evt, t, llnode, list) {
-		vhost_scsi_do_evt_work(vs, evt);
+		if (!drop)
+			vhost_scsi_do_evt_work(vs, evt);
 		vhost_scsi_free_evt(vs, evt);
 	}
 	mutex_unlock(&vq->mutex);
 }
 
+static void vhost_scsi_evt_work(struct vhost_work *work)
+{
+	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
+					     vs_event_work);
+	vhost_scsi_complete_events(vs, false);
+}
+
 static int vhost_scsi_copy_sgl_to_iov(struct vhost_scsi_cmd *cmd)
 {
 	struct iov_iter *iter = &cmd->saved_iter;
@@ -1509,7 +1515,8 @@ vhost_scsi_send_evt(struct vhost_scsi *vs, struct vhost_virtqueue *vq,
 	}
 
 	llist_add(&evt->list, &vs->vs_event_list);
-	vhost_vq_work_queue(vq, &vs->vs_event_work);
+	if (!vhost_vq_work_queue(vq, &vs->vs_event_work))
+		vhost_scsi_complete_events(vs, true);
 }
 
 static void vhost_scsi_evt_handle_kick(struct vhost_work *work)




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