3.16.55-rc1 review patch. If anyone has any objections, please let me know.
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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: Ben Hutchings ben@decadent.org.uk --- 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 @@ -2008,10 +2008,12 @@ 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; }
@@ -3345,7 +3347,7 @@ 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;