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dma_alloc_from_coherent(): fix fallback to generic memory 

If bitmap_find_free_region() fails and DMA_MEMORY_EXCLUSIVE is not set,
the function will fail to write anything to *ret and will return 1.             This will cause dma_alloc_coherent() to return an uninitialised value,
crashing the kernel, perhaps via DMA to a random address.

Fix that by changing it to return zero in this case, so the caller will
proceed to allocate the memory from the generic memory allocator.

Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Dmitry Baryshkov <dbaryshkov@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrew Morton 2009-01-06 14:43:08 -08:00 committed by Linus Torvalds
parent 8375d4909a
commit 0bef3c2dc7
1 changed files with 15 additions and 1 deletions
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16
kernel/dma-coherent.c
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@ -116,11 +116,25 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
int page = bitmap_find_free_region(mem->bitmap, mem->size,
order);
if (page >= 0) {
/*
* Memory was found in the per-device arena.
*/
*dma_handle = mem->device_base + (page << PAGE_SHIFT);
*ret = mem->virt_base + (page << PAGE_SHIFT);
memset(*ret, 0, size);
} else if (mem->flags & DMA_MEMORY_EXCLUSIVE)
} else if (mem->flags & DMA_MEMORY_EXCLUSIVE) {
/*
* The per-device arena is exhausted and we are not
* permitted to fall back to generic memory.
*/
*ret = NULL;
} else {
/*
* The per-device arena is exhausted and we are
* permitted to fall back to generic memory.
*/
return 0;
}
}
return (mem != NULL);
}