linux-kernel - Re: [PATCH v2] drm/amdgpu: fix multiple memory leaks

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Message-ID: <7450dab5-3c3f-0b91-4656-6c5a7cf4d49d@amd.com>
Date:   Thu, 19 Sep 2019 16:48:47 +0000
From:   "Koenig, Christian" <Christian.Koenig@....com>
To:     Sven Van Asbroeck <thesven73@...il.com>
CC:     Navid Emamdoost <navid.emamdoost@...il.com>,
        "emamd001@....edu" <emamd001@....edu>,
        "smccaman@....edu" <smccaman@....edu>,
        "kjlu@....edu" <kjlu@....edu>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Rex Zhu <Rex.Zhu@....com>,
        Sam Ravnborg <sam@...nborg.org>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/amdgpu: fix multiple memory leaks

Am 19.09.19 um 16:28 schrieb Sven Van Asbroeck:
> Hi Christian,
>
> On Thu, Sep 19, 2019 at 4:05 AM Koenig, Christian
> <Christian.Koenig@....com> wrote:
>>> +out4:
>>> +     kfree(i2s_pdata);
>>> +out3:
>>> +     kfree(adev->acp.acp_res);
>>> +out2:
>>> +     kfree(adev->acp.acp_cell);
>>> +out1:
>>> +     kfree(adev->acp.acp_genpd);
>> kfree on a NULL pointer is harmless, so a single error label should be
>> sufficient.
> That is true, but I notice that the adev structure comes from outside this
> driver:

adev is a very integral part of the driver and always zero initialized:

adev = kzalloc(sizeof(struct amdgpu_device), GFP_KERNEL);

Regards,
Christian.

>
> static int acp_hw_init(void *handle)
> {
> ...
> struct amdgpu_device *adev = (struct amdgpu_device *)handle;
> ...
> }
>
> As far as I can tell, the init() does not explicitly set these to NULL:
> adev->acp.acp_res
> adev->acp.acp_cell
> adev->acp.acp_genpd
>
> I am assuming that core code sets these to NULL, before calling
> acp_hw_init(). But is that guaranteed or simply a happy accident?
> Ie. if they are NULL today, are they likely to remain NULL tomorrow?
>
> Because calling kfree() on a stale pointer would be, well
> not good. Especially not on an error path, which typically
> does not receive much testing, if any.
>
> My apologies if I have misinterpreted this, I am not familiar with
> this code base.
>
> Sven