Re: [PATCH net] net: thunderx: Fix format-truncation warning in bgx_acpi_match_id()

[Simon Horman <horms@kernel.org>]

On Sun, Jul 06, 2025 at 12:51:42PM -0700, Alok Tiwari wrote:
> The buffer bgx_sel used in snprintf() was too small to safely hold
> the formatted string "BGX%d" for all valid bgx_id values. This caused
> a -Wformat-truncation warning with Werror enabled during build.
> 
> Increase the buffer size from 5 to 8 and use sizeof(bgx_sel) in
> snprintf() to ensure safety and suppress the warning.
> 
> Build warning:
>   CC      drivers/net/ethernet/cavium/thunder/thunder_bgx.o
>   drivers/net/ethernet/cavium/thunder/thunder_bgx.c: In function
> ‘bgx_acpi_match_id’:
>   drivers/net/ethernet/cavium/thunder/thunder_bgx.c:1434:27: error: ‘%d’
> directive output may be truncated writing between 1 and 3 bytes into a
> region of size 2 [-Werror=format-truncation=]
>     snprintf(bgx_sel, 5, "BGX%d", bgx->bgx_id);
>                              ^~
>   drivers/net/ethernet/cavium/thunder/thunder_bgx.c:1434:23: note:
> directive argument in the range [0, 255]
>     snprintf(bgx_sel, 5, "BGX%d", bgx->bgx_id);
>                          ^~~~~~~
>   drivers/net/ethernet/cavium/thunder/thunder_bgx.c:1434:2: note:
> ‘snprintf’ output between 5 and 7 bytes into a destination of size 5
>     snprintf(bgx_sel, 5, "BGX%d", bgx->bgx_id);
> 
> compiler warning due to insufficient snprintf buffer size.
> 
> Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>

Thanks Alok,

I agree this is a good change.

However, by my reading the range of values of bgx->bgx_id is 0 - 8
because of the application of BGX_ID_MASK which restricts the
value to 3 bits.

If so, I don't think this is a bug and it should be targeted at net-next.
With a description of why it is not a bug.

Conversely, you think it is a bug, then I think an explanation as to why
would be nice to add to the commit description.  And A fixes tag is needed.

-- 
pw-bot: changes-requested