Re: [PATCH] drm/i915/gvt: fix unterminated-string-initialization warning

[Zhenyu Wang <zhenyuw.linux@gmail.com>]

On Thu, Mar 27, 2025 at 02:47:39PM +0200, Jani Nikula wrote:
> 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.
>

Indeed...

> 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 <kees@kernel.org>
> Closes: https://lore.kernel.org/r/20250310222355.work.417-kees@kernel.org
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13934
> Tested-by: Nicolas Chauvet <kwizart@gmail.com>
> Tested-by: Damian Tometzki <damian@riscv-rocks.de>
> Cc: stable@vger.kernel.org
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---

Reviewed-by: Zhenyu Wang <zhenyuw.linux@gmail.com>

>  drivers/gpu/drm/i915/gvt/opregion.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/opregion.c b/drivers/gpu/drm/i915/gvt/opregion.c
> index 509f9ccae3a9..dbad4d853d3a 100644
> --- a/drivers/gpu/drm/i915/gvt/opregion.c
> +++ b/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;
> -- 
> 2.39.5
>