[PATCH v3 1/1] iommu/arm-smmu-v3: eliminate a potential memory corruption on hi1620 and earlier
From: robin.murphy@arm.com (Robin Murphy)
Date: 2018-10-31 11:43:59
Also in:
linux-iommu, lkml
On 31/10/2018 04:02, Zhen Lei wrote:
The standard GITS_TRANSLATER register in ITS is only 4 bytes, but Hisilicon expands the next 4 bytes to carry some IMPDEF information. That means, total 8 bytes data will be written to MSIAddress each time. MSIAddr: |----4bytes----|----4bytes----| | MSIData | IMPDEF | There is no problem for ITS, because the next 4 bytes space is reserved in ITS. But it will overwrite the 4 bytes memory following "sync_count". It's very fortunately that the previous and the next neighbour of the "sync_count" are both aligned by 8 bytes, so no problem is met now. It's good to explicitly add a workaround. Let's enclose the "sync_count" into a union and companion with a new member "padding" of type u64. There is no functional change.
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
quoted hunk ↗ jump to hunk
Signed-off-by: Zhen Lei <redacted> --- drivers/iommu/arm-smmu-v3.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 6947ccf..4e94730 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c@@ -576,7 +576,23 @@ struct arm_smmu_device { struct arm_smmu_strtab_cfg strtab_cfg; - u32 sync_count; + /* + * The member "padding" is used to make sure the member "sync_count" to + * be aligned at 8 bytes boundary, and 4 bytes padding memory followed. + * + * These are required by hi1620 and earlier of Hisilicon. Because the + * ITS hardware on hi1620 and earlier will truncate the MSIAddress(Here + * it's the address of "sync_count") to 8 bytes boundary first, then + * write 32 bits MSIdata at offset 0, and 32 bits IMPDEF data at offset + * 4. Without this workaround, the adjacent member maybe overwritten. + * + * |---4bytes---|---4bytes---| + * MSIAddress & (~0x7): MSIdata | IMPDEF data| + */ + union { + u32 sync_count; + u64 padding; + }; /* IOMMU core code handle */ struct iommu_device iommu; --1.8.3