linux-kernel - Re: [PATCH] drm/amd/amdgpu/amdgpu_ttm: Handle return NULL error from ioremap

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Date:   Tue, 24 Jan 2017 10:55:37 +0100
From:   Christian König <deathsimple@...afone.de>
To:     Arvind Yadav <arvind.yadav.cs@...il.com>, airlied@...ux.ie
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/amd/amdgpu/amdgpu_ttm: Handle return NULL error from
 ioremap_nocache

Am 24.01.2017 um 10:25 schrieb Arvind Yadav:
> Here, If ioremap_nocache will fail. It will return NULL.
> Kernel can run into a NULL-pointer dereference.
> This error check will avoid NULL pointer dereference.
>
> Signed-off-by: Arvind Yadav <arvind.yadav.cs@...il.com>

I'm not 100% sure if ioremap_nocache() can actually return NULL on 
platforms where this matters, but if that's the case the patch looks 
reasonable on first glance.

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

Regards,
Christian.

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 8e35c1f..610c88f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -552,6 +552,8 @@ static int amdgpu_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_mem_
>   			mem->bus.addr =
>   				ioremap_nocache(mem->bus.base + mem->bus.offset,
>   						mem->bus.size);
> +		if (!mem->bus.addr)
> +			return -ENOMEM;
>   
>   		/*
>   		 * Alpha: Use just the bus offset plus