Re: [PATCH v3] sh: mm: Fix unprotected access to struct device

jacopo mondi
2018-05-02T07:46:55Z

[-- Attachment #1: Type: text/plain, Size: 3034 bytes --]

Hi again Christoph,

The gentle ping actually applies to this version of the patch.

Sorry for the confusion.
Thanks
j

On Wed, Apr 18, 2018 at 11:42:35AM +0200, Jacopo Mondi wrote:
> With commit ce88313069c36eef80f21fd7 ("arch/sh: make the DMA mapping
> operations observe dev->dma_pfn_offset") the generic DMA allocation
> function on which the SH 'dma_alloc_coherent()' function relies on,
> accesses the 'dma_pfn_offset' field of struct device.
>
> Unfortunately the 'dma_generic_alloc_coherent()' function is called from
> several places with a NULL struct device argument, halting the CPU
> during the boot process.
>
> This patch fixes the issue by protecting access to dev->dma_pfn_offset,
> with a trivial check for validity. It also passes a valid 'struct device'
> in the 'platform_resource_setup_memory()' function which is the main user
> of 'dma_alloc_coherent()', and inserts a WARN_ON() check to remind to future
> (and existing) bogus users of this function to provide a valid 'struct device'
> whenever possible.
>
> Fixes: ce88313069c36eef80f21fd7 ("arch/sh: make the DMA mapping operations observe dev->dma_pfn_offset")
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Reviewed-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
>
> ---
> v2 -> v3:
> - remove (now) useless parenthesis around pfn assignement as suggested
> by Sergei
> - Add changelog to the patch, which I forgot in v2
>
> v1 -> v2:
> - Move WARN_ON() closer to dev validity check as suggested by Geert
>
> ---
> arch/sh/mm/consistent.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/arch/sh/mm/consistent.c b/arch/sh/mm/consistent.c
> index 8ce9869..f1b4469 100644
> --- a/arch/sh/mm/consistent.c
> +++ b/arch/sh/mm/consistent.c
> @@ -59,7 +59,9 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size,
>
> split_page(pfn_to_page(virt_to_phys(ret) >> PAGE_SHIFT), order);
>
> - *dma_handle = virt_to_phys(ret) - PFN_PHYS(dev->dma_pfn_offset);
> + *dma_handle = virt_to_phys(ret);
> + if (!WARN_ON(!dev))
> + *dma_handle -= PFN_PHYS(dev->dma_pfn_offset);
>
> return ret_nocache;
> }
> @@ -69,9 +71,12 @@ void dma_generic_free_coherent(struct device *dev, size_t size,
> unsigned long attrs)
> {
> int order = get_order(size);
> - unsigned long pfn = (dma_handle >> PAGE_SHIFT) + dev->dma_pfn_offset;
> + unsigned long pfn = dma_handle >> PAGE_SHIFT;
> int k;
>
> + if (!WARN_ON(!dev))
> + pfn += dev->dma_pfn_offset;
> +
> for (k = 0; k < (1 << order); k++)
> __free_pages(pfn_to_page(pfn + k), 0);
>
> @@ -143,7 +148,7 @@ int __init platform_resource_setup_memory(struct platform_device *pdev,
> if (!memsize)
> return 0;
>
> - buf = dma_alloc_coherent(NULL, memsize, &dma_handle, GFP_KERNEL);
> + buf = dma_alloc_coherent(&pdev->dev, memsize, &dma_handle, GFP_KERNEL);
> if (!buf) {
> pr_warning("%s: unable to allocate memory\n", name);
> return -ENOMEM;
> --
> 2.7.4
>

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 819 bytes --]