[PATCH 5.10] vhost-scsi: protect vq->log_used with vq->mutex

[ZHENG Xinyu]

From: Dongli Zhang <dongli.zhang@xxxxxxxxxx>

The vhost-scsi completion path may access vq->log_base when vq->log_used is
already set to false.

    vhost-thread                       QEMU-thread

vhost_scsi_complete_cmd_work()
-> vhost_add_used()
   -> vhost_add_used_n()
      if (unlikely(vq->log_used))
                                      QEMU disables vq->log_used
                                      via VHOST_SET_VRING_ADDR.
                                      mutex_lock(&vq->mutex);
                                      vq->log_used = false now!
                                      mutex_unlock(&vq->mutex);

				      QEMU gfree(vq->log_base)
        log_used()
        -> log_write(vq->log_base)

Assuming the VMM is QEMU. The vq->log_base is from QEMU userpace and can be
reclaimed via gfree(). As a result, this causes invalid memory writes to
QEMU userspace.

The control queue path has the same issue.

Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Reviewed-by: Mike Christie <michael.christie@xxxxxxxxxx>
Message-Id: <20250403063028.16045-2-dongli.zhang@xxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
Signed-off-by: Zheng Xinyu <zhengxinyu6@xxxxxxxxxx>
---
 drivers/vhost/scsi.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index a23a65e7d828..fcde3752b4f1 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -579,8 +579,10 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
 		ret = copy_to_iter(&v_rsp, sizeof(v_rsp), &iov_iter);
 		if (likely(ret == sizeof(v_rsp))) {
 			struct vhost_scsi_virtqueue *q;
-			vhost_add_used(cmd->tvc_vq, cmd->tvc_vq_desc, 0);
 			q = container_of(cmd->tvc_vq, struct vhost_scsi_virtqueue, vq);
+			mutex_lock(&q->vq.mutex);
+			vhost_add_used(cmd->tvc_vq, cmd->tvc_vq_desc, 0);
+			mutex_unlock(&q->vq.mutex);
 			vq = q - vs->vqs;
 			__set_bit(vq, signal);
 		} else
@@ -1193,8 +1195,11 @@ static void vhost_scsi_tmf_resp_work(struct vhost_work *work)
 	else
 		resp_code = VIRTIO_SCSI_S_FUNCTION_REJECTED;
 
+	mutex_lock(&tmf->svq->vq.mutex);
 	vhost_scsi_send_tmf_resp(tmf->vhost, &tmf->svq->vq, tmf->in_iovs,
 				 tmf->vq_desc, &tmf->resp_iov, resp_code);
+	mutex_unlock(&tmf->svq->vq.mutex);
+
 	vhost_scsi_release_tmf_res(tmf);
 }
 
-- 
2.34.1