drm/radeon: check bo_va->bo is non-NULL before using it

jira LE-3201
cve CVE-2024-41060
Rebuild_History Non-Buildable kernel-rt-4.18.0-553.22.1.rt7.363.el8_10
commit-author Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
commit ca280d2

The call to radeon_vm_clear_freed might clear bo_va->bo, so
we have to check it before dereferencing it.

	Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
	Acked-by: Alex Deucher <alexander.deucher@amd.com>
	Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit ca280d2)
	Signed-off-by: Jonathan Maple <jmaple@ciq.com>

Author: PlaidCat

drivers/gpu/drm/radeon/radeon_gem.c

@@ -657,7 +657,7 @@ static void radeon_gem_va_update_vm(struct radeon_device *rdev,
 	if (r)
 		goto error_unlock;
 
-	if (bo_va->it.start)
+	if (bo_va->it.start && bo_va->bo)
 		r = radeon_vm_bo_update(rdev, bo_va, bo_va->bo->tbo.resource);
 
 error_unlock: