linux-kernel - Re: [PATCH][next] amd/amdgpu_ctx: Use struct

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Date:   Fri, 9 Oct 2020 16:29:55 +0200
From:   Christian König <christian.koenig@....com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Alex Deucher <alexander.deucher@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] amd/amdgpu_ctx: Use struct_size() helper and
 kmalloc()

Am 09.10.20 um 15:54 schrieb Gustavo A. R. Silva:
> On Fri, Oct 09, 2020 at 09:08:51AM +0200, Christian König wrote:
>> Am 08.10.20 um 16:34 schrieb Gustavo A. R. Silva:
>>> Make use of the new struct_size() helper instead of the offsetof() idiom.
>>> Also, use kmalloc() instead of kcalloc().
>>>
>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
>>> ---
>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
>>> index c80d8339f58c..5be125f3b92a 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
>>> @@ -100,7 +100,7 @@ static int amdgpu_ctx_init_entity(struct amdgpu_ctx *ctx, u32 hw_ip,
>>>    	enum drm_sched_priority priority;
>>>    	int r;
>>> -	entity = kcalloc(1, offsetof(typeof(*entity), fences[amdgpu_sched_jobs]),
>>> +	entity = kmalloc(struct_size(entity, fences, amdgpu_sched_jobs),
>> NAK. You could use kzalloc() here, but kmalloc won't zero initialize the
>> memory which could result in unforeseen consequences.
> Oh I see.. I certainly didn't take that into account.
>
> I'll fix that up and respin.

Shit happens, we already have a fix for this. Alex merged it and it 
immediately broke our testing systems.

So one of our engineers came up with a fix which should already have 
been applied.

Christian.

>
> Thanks
> --
> Gustavo