linux-hardening - Re: [PATCH] nouveau/gsp: Avoid addressing beyond end of rpc->entries

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Date: Fri, 5 Apr 2024 18:37:26 +0200
From: Danilo Krummrich <dakr@...hat.com>
To: Kees Cook <keescook@...omium.org>
Cc: Lyude Paul <lyude@...hat.com>, David Airlie <airlied@...il.com>,
 Daniel Vetter <daniel@...ll.ch>, Dave Airlie <airlied@...hat.com>,
 Ben Skeggs <bskeggs@...hat.com>, Timur Tabi <ttabi@...dia.com>,
 dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Dan Carpenter <dan.carpenter@...aro.org>, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org, Karol Herbst <kherbst@...hat.com>
Subject: Re: [PATCH] nouveau/gsp: Avoid addressing beyond end of rpc->entries

On 3/30/24 15:12, Kees Cook wrote:
> Using the end of rpc->entries[] for addressing runs into both compile-time
> and run-time detection of accessing beyond the end of the array. Use the
> base pointer instead, since was allocated with the additional bytes for
> storing the strings. Avoids the following warning in future GCC releases
> with support for __counted_by:
> 
> In function 'fortify_memcpy_chk',
>      inlined from 'r535_gsp_rpc_set_registry' at ../drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1123:3:
> ../include/linux/fortify-string.h:553:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
>    553 |                         __write_overflow_field(p_size_field, size);
>        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> for this code:
> 
> 	strings = (char *)&rpc->entries[NV_GSP_REG_NUM_ENTRIES];
> 	...
>                  memcpy(strings, r535_registry_entries[i].name, name_len);
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>

Applied to drm-misc-fixes, thanks!

> ---
> Cc: Karol Herbst <kherbst@...hat.com>
> Cc: Lyude Paul <lyude@...hat.com>
> Cc: Danilo Krummrich <dakr@...hat.com>
> Cc: David Airlie <airlied@...il.com>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: Dave Airlie <airlied@...hat.com>
> Cc: Ben Skeggs <bskeggs@...hat.com>
> Cc: Timur Tabi <ttabi@...dia.com>
> Cc: dri-devel@...ts.freedesktop.org
> Cc: nouveau@...ts.freedesktop.org
> ---
>   drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
> index 9994cbd6f1c4..9858c1438aa7 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
> @@ -1112,7 +1112,7 @@ r535_gsp_rpc_set_registry(struct nvkm_gsp *gsp)
>   	rpc->numEntries = NV_GSP_REG_NUM_ENTRIES;
>   
>   	str_offset = offsetof(typeof(*rpc), entries[NV_GSP_REG_NUM_ENTRIES]);
> -	strings = (char *)&rpc->entries[NV_GSP_REG_NUM_ENTRIES];
> +	strings = (char *)rpc + str_offset;
>   	for (i = 0; i < NV_GSP_REG_NUM_ENTRIES; i++) {
>   		int name_len = strlen(r535_registry_entries[i].name) + 1;
>