drm/i915/gvt: fix unterminated-string-initialization warning

commit 2e43ae7dd71cd9bb0d1bce1d3306bf77523feb81 upstream.

Initializing const char opregion_signature[16] = OPREGION_SIGNATURE
(which is "IntelGraphicsMem") drops the NUL termination of the
string. This is intentional, but the compiler doesn't know this.

Switch to initializing header->signature directly from the string
litaral, with sizeof destination rather than source. We don't treat the
signature as a string other than for initialization; it's really just a
blob of binary data.

Add a static assert for good measure to cross-check the sizes.

Reported-by: Kees Cook <[email protected]>
Closes: https://lore.kernel.org/r/[email protected]
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13934
Tested-by: Nicolas Chauvet <[email protected]>
Tested-by: Damian Tometzki <[email protected]>
Cc: [email protected]
Reviewed-by: Zhenyu Wang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jani Nikula <[email protected]>
(cherry picked from commit 4f8207469094bd04aad952258ceb9ff4c77b6bfa)
Signed-off-by: Jani Nikula <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
(cherry picked from commit 4b171d4cbfffca02df349ed8405e93ff3b01e36a)
Signed-off-by: Jack Vogel <[email protected]>

Author: jnikula

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

@@ -222,7 +222,6 @@ int intel_vgpu_init_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 |
@@ -236,8 +235,10 @@ int intel_vgpu_init_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));
+
+	static_assert(sizeof(header->signature) == sizeof(OPREGION_SIGNATURE) - 1);
+	memcpy(header->signature, OPREGION_SIGNATURE, sizeof(header->signature));
+
 	header->size = 0x8;
 	header->opregion_ver = 0x02000000;
 	header->mboxes = MBOX_VBT;