This is a note to let you know that I've just added the patch titled

iommu/vt-d: Fix scatterlist offset handling

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: iommu-vt-d-fix-scatterlist-offset-handling.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 29a90b70893817e2f2bb3cea40a29f5308e21b21 Mon Sep 17 00:00:00 2001

From: Robin Murphy robin.murphy@arm.com Date: Thu, 28 Sep 2017 15:14:01 +0100 Subject: iommu/vt-d: Fix scatterlist offset handling

From: Robin Murphy robin.murphy@arm.com

commit 29a90b70893817e2f2bb3cea40a29f5308e21b21 upstream.

The intel-iommu DMA ops fail to correctly handle scatterlists where sg->offset is greater than PAGE_SIZE - the IOVA allocation is computed appropriately based on the page-aligned portion of the offset, but the mapping is set up relative to sg->page, which means it fails to actually cover the whole buffer (and in the worst case doesn't cover it at all):

(sg->dma_address + sg->dma_len) ----+ sg->dma_address ---------+ | iov_pfn------+ | | | | | v v v iova: a b c d e f |--------|--------|--------|--------|--------| <...calculated....> [_____mapped______] pfn: 0 1 2 3 4 5 |--------|--------|--------|--------|--------| ^ ^ ^ | | | sg->page ----+ | | sg->offset --------------+ | (sg->offset + sg->length) ----------+

As a result, the caller ends up overrunning the mapping into whatever lies beyond, which usually goes badly:

[ 429.645492] DMAR: DRHD: handling fault status reg 2 [ 429.650847] DMAR: [DMA Write] Request device [02:00.4] fault addr f2682000 ...

Whilst this is a fairly rare occurrence, it can happen from the result of intermediate scatterlist processing such as scatterwalk_ffwd() in the crypto layer. Whilst that particular site could be fixed up, it still seems worthwhile to bring intel-iommu in line with other DMA API implementations in handling this robustly.

To that end, fix the intel_map_sg() path to line up the mapping correctly (in units of MM pages rather than VT-d pages to match the aligned_nrpages() calculation) regardless of the offset, and use sg_phys() consistently for clarity.

Reported-by: Harsh Jain Harsh@chelsio.com Signed-off-by: Robin Murphy robin.murphy@arm.com Reviewed by: Ashok Raj ashok.raj@intel.com Tested by: Jacob Pan jacob.jun.pan@intel.com Signed-off-by: Alex Williamson alex.williamson@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- drivers/iommu/intel-iommu.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/iommu/intel-iommu.c +++ b/drivers/iommu/intel-iommu.c @@ -2254,10 +2254,12 @@ static int __domain_mapping(struct dmar_ uint64_t tmp;

if (!sg_res) { + unsigned int pgoff = sg->offset & ~PAGE_MASK; + sg_res = aligned_nrpages(sg->offset, sg->length); - sg->dma_address = ((dma_addr_t)iov_pfn << VTD_PAGE_SHIFT) + sg->offset; + sg->dma_address = ((dma_addr_t)iov_pfn << VTD_PAGE_SHIFT) + pgoff; sg->dma_length = sg->length; - pteval = page_to_phys(sg_page(sg)) | prot; + pteval = (sg_phys(sg) - pgoff) | prot; phys_pfn = pteval >> VTD_PAGE_SHIFT; }

@@ -3790,7 +3792,7 @@ static int intel_nontranslate_map_sg(str

for_each_sg(sglist, sg, nelems, i) { BUG_ON(!sg_page(sg)); - sg->dma_address = page_to_phys(sg_page(sg)) + sg->offset; + sg->dma_address = sg_phys(sg); sg->dma_length = sg->length; } return nelems;

Patches currently in stable-queue which might be from robin.murphy@arm.com are

queue-4.14/iommu-vt-d-fix-scatterlist-offset-handling.patch