swiotlb: Enforce page alignment in swiotlb_alloc()

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.

Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Petr Tesarik <petr.tesarik1@huawei-partners.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 980a7ec70418eabbc97e4c5f44ad26baa4196a01..88114433f1e69e7720215f9cb5575db0543d6e03 100644 (file)
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1689,6 +1689,12 @@ 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));
 }