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Subject[PATCH v4 2/5] swiotlb: Enforce page alignment in swiotlb_alloc()
Date
When allocating pages from a restricted DMA pool in swiotlb_alloc(),
the buffer address is blindly converted to a 'struct page *' that is
returned to the caller. In the unlikely event of an allocation bug,
page-unaligned addresses are not detected and slots can silently be
double-allocated.

Add a simple check of the buffer alignment in swiotlb_alloc() to make
debugging a little easier if something has gone wonky.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Petr Tesarik <petr.tesarik1@huawei-partners.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
kernel/dma/swiotlb.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 2ec2cc81f1a2..ab7fbb40bc55 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1643,6 +1643,12 @@ struct page *swiotlb_alloc(struct device *dev, size_t size)
return NULL;

tlb_addr = slot_addr(pool->start, index);
+ if (unlikely(!PAGE_ALIGNED(tlb_addr))) {
+ dev_WARN_ONCE(dev, 1, "Cannot allocate pages from non page-aligned swiotlb addr 0x%pa.\n",
+ &tlb_addr);
+ swiotlb_release_slots(dev, tlb_addr);
+ return NULL;
+ }

return pfn_to_page(PFN_DOWN(tlb_addr));
}
--
2.44.0.rc0.258.g7320e95886-goog

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