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

[Jacopo Mondi]

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+rene...@jmondi.org>
Reviewed-by: Geert Uytterhoeven <geert+rene...@glider.be>
Reviewed-by: Thomas Petazzoni <thomas.petazz...@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