linux-kernel - Re: [PATCH net-next v2] net: thunderx: Fix format-truncation warning in bgx_acpi_match

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Message-ID: <20250710153422.6adae255@kernel.org>
Date: Thu, 10 Jul 2025 15:34:22 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Alok Tiwari <alok.a.tiwari@...cle.com>
Cc: sgoutham@...vell.com, andrew+netdev@...n.ch, davem@...emloft.net,
 edumazet@...gle.com, pabeni@...hat.com, horms@...nel.org,
 netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 darren.kenny@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2] net: thunderx: Fix format-truncation
 warning in bgx_acpi_match_id()

On Tue,  8 Jul 2025 10:52:43 -0700 Alok Tiwari wrote:
> 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);

Hm, why are you making it 8 when the max length is 7 ? 🤔️
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