Commit 0bef3c2d authored Jan 06, 2009 by Andrew Morton Committed by Linus Torvalds Jan 06, 2009

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>

parent 8375d490

kernel/dma-coherent.c

+15 −1

Original line number	Diff line number	Diff line
		@@ -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);
		}

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