[PATCH] fbdev: Replace 0-length array with flexible array

[PATCH] fbdev: Replace 0-length array with flexible array

[Kees Cook]

Zero-length arrays are deprecated[1]. Replace struct aperture's "ranges"
0-length array with a flexible array. (How is the size of this array
verified?) Detected with GCC 13, using -fstrict-flex-arrays=3:

samples/vfio-mdev/mdpy-fb.c: In function 'mdpy_fb_probe':
samples/vfio-mdev/mdpy-fb.c:169:32: warning: array subscript 0 is outside array bounds of 'struct aperture[0]' [-Warray-bounds=]
  169 |         info->apertures->ranges[0].base = info->fix.smem_start;
      |         ~~~~~~~~~~~~~~~~~~~~~~~^~~
In file included from samples/vfio-mdev/mdpy-fb.c:21:
include/linux/fb.h:510:19: note: while referencing 'ranges'
  510 |                 } ranges[0];
      |                   ^~~~~~

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays

Cc: Helge Deller <deller@gmx.de>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: linux-fbdev@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/fb.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/fb.h b/include/linux/fb.h
index 96b96323e9cb..bf59d6a3590f 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -507,7 +507,7 @@ struct fb_info {
 		struct aperture {
 			resource_size_t base;
 			resource_size_t size;
-		} ranges[0];
+		} ranges[];
 	} *apertures;
 
 	bool skip_vt_switch; /* no VT switch on suspend/resume required */
-- 
2.34.1

Re: [PATCH] fbdev: Replace 0-length array with flexible array

[Gustavo A. R. Silva]

On Thu, Jan 05, 2023 at 11:20:38AM -0800, Kees Cook wrote:
> Zero-length arrays are deprecated[1]. Replace struct aperture's "ranges"
> 0-length array with a flexible array. (How is the size of this array
> verified?) Detected with GCC 13, using -fstrict-flex-arrays=3:
> 
> samples/vfio-mdev/mdpy-fb.c: In function 'mdpy_fb_probe':
> samples/vfio-mdev/mdpy-fb.c:169:32: warning: array subscript 0 is outside array bounds of 'struct aperture[0]' [-Warray-bounds=]
>   169 |         info->apertures->ranges[0].base = info->fix.smem_start;
>       |         ~~~~~~~~~~~~~~~~~~~~~~~^~~
> In file included from samples/vfio-mdev/mdpy-fb.c:21:
> include/linux/fb.h:510:19: note: while referencing 'ranges'
>   510 |                 } ranges[0];
>       |                   ^~~~~~
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Cc: Helge Deller <deller@gmx.de>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: linux-fbdev@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks!
--
Gustavo

> ---
>  include/linux/fb.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 96b96323e9cb..bf59d6a3590f 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -507,7 +507,7 @@ struct fb_info {
>  		struct aperture {
>  			resource_size_t base;
>  			resource_size_t size;
> -		} ranges[0];
> +		} ranges[];
>  	} *apertures;
>  
>  	bool skip_vt_switch; /* no VT switch on suspend/resume required */
> -- 
> 2.34.1
> 

Re: [PATCH] fbdev: Replace 0-length array with flexible array

[Helge Deller]

On 1/5/23 20:20, Kees Cook wrote:
> Zero-length arrays are deprecated[1]. Replace struct aperture's "ranges"
> 0-length array with a flexible array. (How is the size of this array
> verified?) Detected with GCC 13, using -fstrict-flex-arrays=3:
>
> samples/vfio-mdev/mdpy-fb.c: In function 'mdpy_fb_probe':
> samples/vfio-mdev/mdpy-fb.c:169:32: warning: array subscript 0 is outside array bounds of 'struct aperture[0]' [-Warray-bounds=]
>    169 |         info->apertures->ranges[0].base = info->fix.smem_start;
>        |         ~~~~~~~~~~~~~~~~~~~~~~~^~~
> In file included from samples/vfio-mdev/mdpy-fb.c:21:
> include/linux/fb.h:510:19: note: while referencing 'ranges'
>    510 |                 } ranges[0];
>        |                   ^~~~~~
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
>
> Cc: Helge Deller <deller@gmx.de>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: linux-fbdev@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

applied to the fbdev git tree.

Thanks!
Helge

> ---
>   include/linux/fb.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 96b96323e9cb..bf59d6a3590f 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -507,7 +507,7 @@ struct fb_info {
>   		struct aperture {
>   			resource_size_t base;
>   			resource_size_t size;
> -		} ranges[0];
> +		} ranges[];
>   	} *apertures;
>
>   	bool skip_vt_switch; /* no VT switch on suspend/resume required */