diff --git a/drivers/gpu/drm/vc4/vc4_bo.c b/drivers/gpu/drm/vc4/vc4_bo.c
index 9006b9861c90..437084f7973c 100644
--- a/drivers/gpu/drm/vc4/vc4_bo.c
+++ b/drivers/gpu/drm/vc4/vc4_bo.c
@@ -719,12 +719,15 @@ int vc4_mmap(struct file *filp, struct vm_area_struct *vma)
 		return -EINVAL;
 	}
 
+	mutex_lock(&bo->madv_lock);
 	if (bo->madv != VC4_MADV_WILLNEED) {
 		DRM_DEBUG("mmaping of %s BO not allowed\n",
 			  bo->madv == VC4_MADV_DONTNEED ?
 			  "purgeable" : "purged");
+		mutex_unlock(&bo->madv_lock);
 		return -EINVAL;
 	}
+	mutex_unlock(&bo->madv_lock);
 
 	/*
 	 * Clear the VM_PFNMAP flag that was set by drm_gem_mmap(), and set the