linux-kernel - [PATCH v3 3/3] swiotlb: Honour dma_alloc_coherent() alignment in swiotlb

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20240205190127.20685-4-will@kernel.org>
Date: Mon,  5 Feb 2024 19:01:27 +0000
From: Will Deacon <will@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: kernel-team@...roid.com,
	Will Deacon <will@...nel.org>,
	iommu@...ts.linux.dev,
	Christoph Hellwig <hch@....de>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Robin Murphy <robin.murphy@....com>,
	Petr Tesarik <petr.tesarik1@...wei-partners.com>,
	Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH v3 3/3] swiotlb: Honour dma_alloc_coherent() alignment in swiotlb_alloc()

core-api/dma-api-howto.rst states the following properties of
dma_alloc_coherent():

  | The CPU virtual address and the DMA address are both guaranteed to
  | be aligned to the smallest PAGE_SIZE order which is greater than or
  | equal to the requested size.

However, swiotlb_alloc() passes zero for the 'alloc_align_mask'
parameter of swiotlb_find_slots() and so this property is not upheld.
Instead, allocations larger than a page are aligned to PAGE_SIZE,

Calculate the mask corresponding to the page order suitable for holding
the allocation and pass that to swiotlb_find_slots().

Cc: Christoph Hellwig <hch@....de>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Robin Murphy <robin.murphy@....com>
Cc: Petr Tesarik <petr.tesarik1@...wei-partners.com>
Cc: Dexuan Cui <decui@...rosoft.com>
Fixes: e81e99bacc9f ("swiotlb: Support aligned swiotlb buffers")
Signed-off-by: Will Deacon <will@...nel.org>
---
 kernel/dma/swiotlb.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index adbb3143238b..283eea33dd22 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1633,12 +1633,14 @@ struct page *swiotlb_alloc(struct device *dev, size_t size)
 	struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
 	struct io_tlb_pool *pool;
 	phys_addr_t tlb_addr;
+	unsigned int align;
 	int index;
 
 	if (!mem)
 		return NULL;
 
-	index = swiotlb_find_slots(dev, 0, size, 0, &pool);
+	align = (1 << (get_order(size) + PAGE_SHIFT)) - 1;
+	index = swiotlb_find_slots(dev, 0, size, align, &pool);
 	if (index == -1)
 		return NULL;
 
-- 
2.43.0.594.gd9cf4e227d-goog