From: Robin Murphy Date: Fri, 4 Dec 2015 17:52:58 +0000 (+0000) Subject: iommu/io-pgtable-arm: Avoid dereferencing bogus PTEs X-Git-Tag: v4.5-rc1~61^2^6^2~6 X-Git-Url: https://git.kernelconcepts.de/?p=karo-tx-linux.git;a=commitdiff_plain;h=2eb97c78613082f308c0b39366c034cb589b8ee9 iommu/io-pgtable-arm: Avoid dereferencing bogus PTEs In the case of corrupted page tables, or when an invalid size is given, __arm_lpae_unmap() may recurse beyond the maximum number of levels. Unfortunately the detection of this error condition only happens *after* calculating a nonsense offset from something which might not be a valid table pointer and dereferencing that to see if it is a valid PTE. Make things a little more robust by checking the level is valid before doing anything which depends on it being so. Reviewed-by: Laurent Pinchart Signed-off-by: Robin Murphy Signed-off-by: Will Deacon --- diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c index 7df97777662d..366a354c689d 100644 --- a/drivers/iommu/io-pgtable-arm.c +++ b/drivers/iommu/io-pgtable-arm.c @@ -486,11 +486,13 @@ static int __arm_lpae_unmap(struct arm_lpae_io_pgtable *data, void *cookie = data->iop.cookie; size_t blk_size = ARM_LPAE_BLOCK_SIZE(lvl, data); + /* Something went horribly wrong and we ran out of page table */ + if (WARN_ON(lvl == ARM_LPAE_MAX_LEVELS)) + return 0; + ptep += ARM_LPAE_LVL_IDX(iova, lvl, data); pte = *ptep; - - /* Something went horribly wrong and we ran out of page table */ - if (WARN_ON(!pte || (lvl == ARM_LPAE_MAX_LEVELS))) + if (WARN_ON(!pte)) return 0; /* If the size matches this level, we're in the right place */