From mboxrd@z Thu Jan 1 00:00:00 1970 From: thunder.leizhen@huawei.com (Leizhen (ThunderTown)) Date: Tue, 16 Oct 2018 18:02:41 +0800 Subject: [PATCH 1/1] iommu/arm-smmu-v3: eliminate a potential memory corruption on Hi16xx soc In-Reply-To: <20181015124617.GA12972@e119886-lin.cambridge.arm.com> References: <1539592576-24352-1-git-send-email-thunder.leizhen@huawei.com> <20181015124617.GA12972@e119886-lin.cambridge.arm.com> Message-ID: <5BC5B741.4020801@huawei.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 2018/10/15 20:46, Andrew Murray wrote: > Hi Zhen, > > On Mon, Oct 15, 2018 at 04:36:16PM +0800, Zhen Lei wrote: >> ITS translation register map: >> 0x0000-0x003C Reserved >> 0x0040 GITS_TRANSLATER >> 0x0044-0xFFFC Reserved >> >> 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, 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 >> luckly that the previous and the next neighbour of "sync_count" are both aligned >> by 8 bytes, so no problem is met now. > > My understanding is that MSI's are 32bit memory writes and as such the SMMU > performs a 32bit write in response to the MSI. If so then what is different > with the Hi16xx that causes a problem? Have you been able to able to adjust > the layout of the arm_smmu_device struct to demonstrate this? In normal, only 32bits MSIdata will be written into sync_count: |----4bytes----|----4bytes----| | sync_count | xxxx | But for Hi16xx, the ITS hardware will write extra 32bits IMDDEF data into "xxxx". If "xxxx" is the space of the next struct member, its value will be overwritten. > > Thanks, > > Andrew Murray > >> >> It's good to explicitly add a workaround: >> 1. Add gcc __attribute__((aligned(8))) to make sure that "sync_count" is always >> aligned by 8 bytes. >> 2. Add a "u64" union member to make sure the 4 bytes padding is always exist. >> >> There is no functional change. >> >> Signed-off-by: Zhen Lei >> --- >> drivers/iommu/arm-smmu-v3.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c >> index 5059d09..a07bc0d 100644 >> --- a/drivers/iommu/arm-smmu-v3.c >> +++ b/drivers/iommu/arm-smmu-v3.c >> @@ -586,7 +586,10 @@ struct arm_smmu_device { >> >> struct arm_smmu_strtab_cfg strtab_cfg; >> >> + union { >> + u64 padding; /* workaround for Hisilicon */ >> u32 sync_count; >> + } __attribute__((aligned(8))); >> >> /* IOMMU core code handle */ >> struct iommu_device iommu; >> -- >> 1.8.3 >> >> >> _______________________________________________ >> iommu mailing list >> iommu at lists.linux-foundation.org >> https://lists.linuxfoundation.org/mailman/listinfo/iommu > > . > -- Thanks! BestRegards