linux-kernel - Re: [PATCH] amdgpu: fix integer overflow on 32-bit architectures

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Date:   Tue, 5 May 2020 16:16:57 +0200
From:   Christian König <christian.koenig@....com>
To:     Arnd Bergmann <arnd@...db.de>,
        Alex Deucher <alexander.deucher@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Evan Quan <evan.quan@....com>
Cc:     Hawking Zhang <Hawking.Zhang@....com>,
        Andrey Grodzovsky <andrey.grodzovsky@....com>,
        Monk Liu <Monk.Liu@....com>,
        Kent Russell <kent.russell@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] amdgpu: fix integer overflow on 32-bit architectures

Am 05.05.20 um 16:15 schrieb Arnd Bergmann:
> Multiplying 1000000000 by four overruns a 'long' variable, as clang
> points out:
>
> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c:4160:53: error: overflow in expression; result is -294967296 with type 'long' [-Werror,-Winteger-overflow]
>                  expires = ktime_get_mono_fast_ns() + NSEC_PER_SEC * 4L;
>                                                                    ^
> Make this a 'long long' constant instead.
>
> Fixes: 3f12acc8d6d4 ("drm/amdgpu: put the audio codec into suspend state before gpu reset V3")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Christian König <christian.koenig@....com>

> ---
> I'm not sure the ktime_get_mono_fast_ns() call is necessary here
> either. Is it intentional because ktime_get_ns() doesn't work
> during a driver suspend, or just a mistake?
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 6f93af972b0a..2e07e3e6b036 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -4157,7 +4157,7 @@ static int amdgpu_device_suspend_display_audio(struct amdgpu_device *adev)
>   		 * the audio controller default autosuspend delay setting.
>   		 * 4S used here is guaranteed to cover that.
>   		 */
> -		expires = ktime_get_mono_fast_ns() + NSEC_PER_SEC * 4L;
> +		expires = ktime_get_mono_fast_ns() + NSEC_PER_SEC * 4LL;
>   
>   	while (!pm_runtime_status_suspended(&(p->dev))) {
>   		if (!pm_runtime_suspend(&(p->dev)))