drm/i915/gvt: Fix out-of-bounds buffer write into opregion->signature[]

sparse spots

drivers/gpu/drm/i915/gvt/opregion.c:234 alloc_and_init_virt_opregion() error: memcpy() 'header->signature' too small (16 vs 17)

as gvt is indeed trying to memcpy a string longer than the signature[].

Fixes: b2d6ef70614e ("drm/i915/gvt: Let each vgpu has separate opregion memory")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Xiong Zhang <xiong.y.zhang@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Cc: intel-gvt-dev@lists.freedesktop.org
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/opregion.c

@@ -218,6 +218,7 @@ static int alloc_and_init_virt_opregion(struct intel_vgpu *vgpu)
 	u8 *buf;
 	struct opregion_header *header;
 	struct vbt v;
+	const char opregion_signature[16] = OPREGION_SIGNATURE;
 
 	gvt_dbg_core("init vgpu%d opregion\n", vgpu->id);
 	vgpu_opregion(vgpu)->va = (void *)__get_free_pages(GFP_KERNEL |
@@ -231,8 +232,8 @@ static int alloc_and_init_virt_opregion(struct intel_vgpu *vgpu)
 	/* emulated opregion with VBT mailbox only */
 	buf = (u8 *)vgpu_opregion(vgpu)->va;
 	header = (struct opregion_header *)buf;
-	memcpy(header->signature, OPREGION_SIGNATURE,
-			sizeof(OPREGION_SIGNATURE));
+	memcpy(header->signature, opregion_signature,
+	       sizeof(opregion_signature));
 	header->size = 0x8;
 	header->opregion_ver = 0x02000000;
 	header->mboxes = MBOX_VBT;