virtio_pci: Fix admin vq cleanup by using correct info pointer

vp_modern_avq_cleanup() and vp_del_vqs() clean up admin vq
resources by virtio_pci_vq_info pointer. The info pointer of admin
vq is stored in vp_dev->admin_vq.info instead of vp_dev->vqs[].
Using the info pointer from vp_dev->vqs[] for admin vq causes a
kernel NULL pointer dereference bug.
In vp_modern_avq_cleanup() and vp_del_vqs(), get the info pointer
from vp_dev->admin_vq.info for admin vq to clean up the resources.
Also make info ptr as argument of vp_del_vq() to be symmetric with
vp_setup_vq().

vp_reset calls vp_modern_avq_cleanup, and causes the Call Trace:
==================================================================
BUG: kernel NULL pointer dereference, address:0000000000000000
...
CPU: 49 UID: 0 PID: 4439 Comm: modprobe Not tainted 6.11.0-rc5 #1
RIP: 0010:vp_reset+0x57/0x90 [virtio_pci]
Call Trace:
<TASK>
...
? vp_reset+0x57/0x90 [virtio_pci]
? vp_reset+0x38/0x90 [virtio_pci]
virtio_reset_device+0x1d/0x30
remove_vq_common+0x1c/0x1a0 [virtio_net]
virtnet_remove+0xa1/0xc0 [virtio_net]
virtio_dev_remove+0x46/0xa0
...
virtio_pci_driver_exit+0x14/0x810 [virtio_pci]
==================================================================

Fixes: 4c3b54af907e ("virtio_pci_modern: use completion instead of busy loop to wait on admin cmd result")
Signed-off-by: Feng Liu <[e-mail]>
Signed-off-by: Jiri Pirko <[e-mail]>
Reviewed-by: Parav Pandit <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>

drivers/virtio/virtio_pci_common.c

···
 		 "Force legacy mode for transitional virtio 1 devices");
 #endif
 
+bool vp_is_avq(struct virtio_device *vdev, unsigned int index)
+{
+	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+
+	if (!virtio_has_feature(vdev, VIRTIO_F_ADMIN_VQ))
+		return false;
+
+	return index == vp_dev->admin_vq.vq_index;
+}
+
 /* wait for pending irq handlers */
 void vp_synchronize_vectors(struct virtio_device *vdev)
 {
···
 	return vq;
 }
 
-static void vp_del_vq(struct virtqueue *vq)
+static void vp_del_vq(struct virtqueue *vq, struct virtio_pci_vq_info *info)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
-	struct virtio_pci_vq_info *info = vp_dev->vqs[vq->index];
 	unsigned long flags;
 
 	/*
···
 void vp_del_vqs(struct virtio_device *vdev)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+	struct virtio_pci_vq_info *info;
 	struct virtqueue *vq, *n;
 	int i;
 
 	list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
-		if (vp_dev->per_vq_vectors) {
-			int v = vp_dev->vqs[vq->index]->msix_vector;
+		info = vp_is_avq(vdev, vq->index) ? vp_dev->admin_vq.info :
+						    vp_dev->vqs[vq->index];
 
+		if (vp_dev->per_vq_vectors) {
+			int v = info->msix_vector;
 			if (v != VIRTIO_MSI_NO_VECTOR &&
 			    !vp_is_slow_path_vector(v)) {
 				int irq = pci_irq_vector(vp_dev->pci_dev, v);
···
 				free_irq(irq, vq);
 			}
 		}
-		vp_del_vq(vq);
+		vp_del_vq(vq, info);
 	}
 	vp_dev->per_vq_vectors = false;
 
···
 			  vring_interrupt, 0,
 			  vp_dev->msix_names[msix_vec], vq);
 	if (err) {
-		vp_del_vq(vq);
+		vp_del_vq(vq, *p_info);
 		return ERR_PTR(err);
 	}
 

drivers/virtio/virtio_pci_common.h

···
 #define VIRTIO_ADMIN_CMD_BITMAP 0
 #endif
 
+bool vp_is_avq(struct virtio_device *vdev, unsigned int index);
 void vp_modern_avq_done(struct virtqueue *vq);
 int vp_modern_admin_cmd_exec(struct virtio_device *vdev,
 			     struct virtio_admin_cmd *cmd);

drivers/virtio/virtio_pci_modern.c

···
 	return 0;
 }
 
-static bool vp_is_avq(struct virtio_device *vdev, unsigned int index)
-{
-	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
-
-	if (!virtio_has_feature(vdev, VIRTIO_F_ADMIN_VQ))
-		return false;
-
-	return index == vp_dev->admin_vq.vq_index;
-}
-
 void vp_modern_avq_done(struct virtqueue *vq)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
···
 	if (!virtio_has_feature(vdev, VIRTIO_F_ADMIN_VQ))
 		return;
 
-	vq = vp_dev->vqs[vp_dev->admin_vq.vq_index]->vq;
+	vq = vp_dev->admin_vq.info->vq;
 	if (!vq)
 		return;