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

[Jani Nikula <jani.nikula@intel.com>]

On Sun, 30 Mar 2025, Zhenyu Wang <zhenyuw.linux@gmail.com> wrote:
> 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>

Thanks for the review, pushed to din.

BR,
Jani.

>
>>  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
>> 

-- 
Jani Nikula, Intel