linux-kernel - Re: [PATCH] drm/ttm: dma: Don't crash on memory in the vmalloc range

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Date:	Fri, 15 May 2015 15:55:51 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Alexandre Courbot <acourbot@...dia.com>
Cc:	Thierry Reding <thierry.reding@...il.com>,
	Thomas Hellstrom <thellstrom@...are.com>,
	Arnd Bergmann <arnd@...db.de>, David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	gnurou@...il.com
Subject: Re: [PATCH] drm/ttm: dma: Don't crash on memory in the vmalloc range

On Fri, May 15, 2015 at 04:09:54PM +0900, Alexandre Courbot wrote:
> dma_alloc_coherent() can return memory in the vmalloc range.
> virt_to_page() cannot handle such addresses and crashes. This
> patch detects such cases and obtains the struct page * using
> vmalloc_to_page() instead.
> 
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> ---
> This patch is a follow-up of the following discussion:
> 
> https://www.marc.info/?l=dri-devel&m=141579595431254&w=3
> 
> It works for me on both 32-bit and 64-bit Tegra, so I am not convinced
> that Thierry's initial change from virt_to_page() to phys_to_page() is
> still required - Thierry, can you confirm whether your patch is still
> relevant after this one?
> 
>  drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> index 01e1d27eb078..3077f1554099 100644
> --- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> +++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> @@ -342,9 +342,12 @@ static struct dma_page *__ttm_dma_alloc_page(struct dma_pool *pool)
>  	d_page->vaddr = dma_alloc_coherent(pool->dev, pool->size,
>  					   &d_page->dma,
>  					   pool->gfp_flags);
> -	if (d_page->vaddr)
> -		d_page->p = virt_to_page(d_page->vaddr);
> -	else {
> +	if (d_page->vaddr) {
> +		if (is_vmalloc_addr(d_page->vaddr))
> +			d_page->p = vmalloc_to_page(d_page->vaddr);
> +		else
> +			d_page->p = virt_to_page(d_page->vaddr);
> +	} else {


Looks OK to me.

>  		kfree(d_page);
>  		d_page = NULL;
>  	}
> -- 
> 2.4.0
> 
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