linux-kernel - Re: [PATCH] drm/amd/pm/smu11: Prevent division by zero

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Message-ID: <CADnq5_O+TMVD0B28Q6CgzhAi1aDR5ofjogE18HDXrJOJ1XwbDQ@mail.gmail.com>
Date: Thu, 20 Mar 2025 09:51:32 -0400
From: Alex Deucher <alexdeucher@...il.com>
To: Denis Arefev <arefev@...mel.ru>
Cc: Kenneth Feng <kenneth.feng@....com>, Alex Deucher <alexander.deucher@....com>, 
	Christian König <christian.koenig@....com>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Lijo Lazar <lijo.lazar@....com>, 
	Ma Jun <Jun.Ma2@....com>, Mario Limonciello <mario.limonciello@....com>, 
	Srinivasan Shanmugam <srinivasan.shanmugam@....com>, Yang Wang <kevinyang.wang@....com>, 
	amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH] drm/amd/pm/smu11: Prevent division by zero

On Thu, Mar 20, 2025 at 9:11 AM Denis Arefev <arefev@...mel.ru> wrote:
>
> The user can set any speed value.
> If speed is greater than UINT_MAX/8, division by zero is possible.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Fixes: 1e866f1fe528 ("drm/amd/pm: Prevent divide by zero")
> Signed-off-by: Denis Arefev <arefev@...mel.ru>

Thanks.  While you are at it, can you fix up all of the other fan
speed cases?  I quick grep shows:
drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c:    tach_period = 60 * xclk
* 10000 / (8 * speed);
drivers/gpu/drm/amd/pm/powerplay/hwmgr/smu7_thermal.c:    tach_period
= 60 * crystal_clock_freq * 10000 / (8 * speed);
drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega20_thermal.c:
tach_period = 60 * crystal_clock_freq * 10000 / (8 * speed);
drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_thermal.c:
tach_period = 60 * crystal_clock_freq * 10000 / (8 * speed);
drivers/gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c:    tach_period = 60
* crystal_clock_freq * 10000 / (8 * speed);
drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c:    tach_period = 60 *
crystal_clock_freq * 10000 / (8 * speed);
drivers/gpu/drm/amd/pm/swsmu/smu13/smu_v13_0.c:    tach_period = 60 *
crystal_clock_freq * 10000 / (8 * speed);

Thanks,

Alex

> ---
>  drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c b/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c
> index 189c6a32b6bd..54229b991858 100644
> --- a/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c
> +++ b/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c
> @@ -1200,7 +1200,7 @@ int smu_v11_0_set_fan_speed_rpm(struct smu_context *smu,
>         uint32_t crystal_clock_freq = 2500;
>         uint32_t tach_period;
>
> -       if (speed == 0)
> +       if (!speed || speed > UINT_MAX/8)
>                 return -EINVAL;
>         /*
>          * To prevent from possible overheat, some ASICs may have requirement
> --
> 2.43.0
>