linux-kernel - Re: [PATCH] drm/amdgpu: off by on in amdgpu_device_attr_create

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Date:   Wed, 20 May 2020 14:05:19 +0200
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Alex Deucher <alexander.deucher@....com>,
        Kevin Wang <kevin1.wang@....com>
Cc:     David Airlie <airlied@...ux.ie>, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        Hawking Zhang <Hawking.Zhang@....com>,
        Rui Huang <ray.huang@....com>, dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel@...ll.ch>, Evan Quan <evan.quan@....com>,
        Kenneth Feng <kenneth.feng@....com>,
        Christian König <christian.koenig@....com>,
        Yintian Tao <yttao@....com>
Subject: Re: [PATCH] drm/amdgpu: off by on in
 amdgpu_device_attr_create_groups() error handling

Am 20.05.20 um 14:00 schrieb Dan Carpenter:
> This loop in the error handling code should start a "i - 1" and end at
> "i == 0".  Currently it starts a "i" and ends at "i == 1".  The result
> is that it removes one attribute that wasn't created yet, and leaks the
> zeroeth attribute.
>
> Fixes: 4e01847c38f7 ("drm/amdgpu: optimize amdgpu device attribute code")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
> index b75362bf0742..ee4a8e44fbeb 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
> @@ -1931,7 +1931,7 @@ static int amdgpu_device_attr_create_groups(struct amdgpu_device *adev,
>   					    uint32_t mask)
>   {
>   	int ret = 0;
> -	uint32_t i = 0;
> +	int i;
>   
>   	for (i = 0; i < counts; i++) {
>   		ret = amdgpu_device_attr_create(adev, &attrs[i], mask);
> @@ -1942,9 +1942,8 @@ static int amdgpu_device_attr_create_groups(struct amdgpu_device *adev,
>   	return 0;
>   
>   failed:
> -	for (; i > 0; i--) {
> +	while (--i >= 0)

As far as I know the common idiom for this is while (i--) which even 
works without changing the type of i to signed.

Christian.

>   		amdgpu_device_attr_remove(adev, &attrs[i]);
> -	}
>   
>   	return ret;
>   }