linux-kernel - Re: [PATCH 15/20] drm/tegra/hub: Increase buffer size to ensure all possible values can be stored

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Message-ID: <ZOciEaJlHhp4xnFv@orome>
Date:   Thu, 24 Aug 2023 11:25:37 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Lee Jones <lee@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Mikko Perttunen <mperttunen@...dia.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH 15/20] drm/tegra/hub: Increase buffer size to ensure all
 possible values can be stored

On Thu, Aug 24, 2023 at 08:37:00AM +0100, Lee Jones wrote:
> When converting from int to string, we must allow for up to 10-chars (2147483647).
> 
> Fixes the following W=1 kernel build warning(s):
> 
>  drivers/gpu/drm/tegra/hub.c: In function ‘tegra_display_hub_probe’:
>  drivers/gpu/drm/tegra/hub.c:1106:47: warning: ‘%u’ directive output may be truncated writing between 1 and 10 bytes into a region of size 4 [-Wformat-truncation=]
>  drivers/gpu/drm/tegra/hub.c:1106:42: note: directive argument in the range [0, 4294967294]
>  drivers/gpu/drm/tegra/hub.c:1106:17: note: ‘snprintf’ output between 6 and 15 bytes into a destination of size 8

I wish there was (perhaps there is?) a better way to annotate that i
will always be within a given range. In practice this is always going to
be smaller than 10 and even in future hardware I wouldn't expect this to
ever exceed anything like 32 or 64, so 8 characters is already generous.

Thierry

> 
> Signed-off-by: Lee Jones <lee@...nel.org>
> ---
> Cc: Thierry Reding <thierry.reding@...il.com>
> Cc: Mikko Perttunen <mperttunen@...dia.com>
> Cc: David Airlie <airlied@...il.com>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: Jonathan Hunter <jonathanh@...dia.com>
> Cc: Philipp Zabel <p.zabel@...gutronix.de>
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linux-tegra@...r.kernel.org
> ---
>  drivers/gpu/drm/tegra/hub.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/tegra/hub.c b/drivers/gpu/drm/tegra/hub.c
> index 1af5f8318d914..f21e57e8599ee 100644
> --- a/drivers/gpu/drm/tegra/hub.c
> +++ b/drivers/gpu/drm/tegra/hub.c
> @@ -1101,7 +1101,7 @@ static int tegra_display_hub_probe(struct platform_device *pdev)
>  
>  	for (i = 0; i < hub->soc->num_wgrps; i++) {
>  		struct tegra_windowgroup *wgrp = &hub->wgrps[i];
> -		char id[8];
> +		char id[16];
>  
>  		snprintf(id, sizeof(id), "wgrp%u", i);
>  		mutex_init(&wgrp->lock);
> -- 
> 2.42.0.rc1.204.g551eb34607-goog
> 

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