From mboxrd@z Thu Jan 1 00:00:00 1970 From: thunder.leizhen@huawei.com (Leizhen (ThunderTown)) Date: Tue, 16 Oct 2018 17:19:14 +0800 Subject: [PATCH 1/1] iommu/arm-smmu-v3: eliminate a potential memory corruption on Hi16xx soc In-Reply-To: <4583617a-49ad-00b5-97fc-1ea35568c5cd@huawei.com> References: <1539592576-24352-1-git-send-email-thunder.leizhen@huawei.com> <4583617a-49ad-00b5-97fc-1ea35568c5cd@huawei.com> Message-ID: <5BC5AD12.1010701@huawei.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 2018/10/15 19:17, John Garry wrote: > On 15/10/2018 09:36, Zhen Lei wrote: >> ITS translation register map: >> 0x0000-0x003C Reserved >> 0x0040 GITS_TRANSLATER >> 0x0044-0xFFFC Reserved >> > > Can you add a better opening than the ITS translation register map? OK > >> 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 > > I think arm_smmu_device.sync_count is better, or "sync_count member in the the smmu driver control struct". OK, I will use "struct" in v2. + struct { u32 sync_count; + u32 padding; + } __attribute__((aligned(8))); > >> luckly that the previous and the next neighbour of "sync_count" are both aligned > > /s/luckly/luckily or fortunately/ OK, thanks > >> by 8 bytes, so no problem is met now. >> >> 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 */ > > I think that a more detailed comment is required. OK, I will try to describe it more clearly. > >> u32 sync_count; > > Can you indent these 2 members? However - as discussed internally - this may have endian issue so better to declare full 64b struct. These indent is inherited, to keep aligning with other members. There is no endian issue, I have tested it on both little-endian and big-endian. $gdb vmlinux ...... (gdb) p &((struct arm_smmu_device *)0)->sync_count $1 = (u32 *) 0x4178 (gdb) p &((struct arm_smmu_device *)0)->tst1 $2 = (int *) 0x4170 (gdb) p &((struct arm_smmu_device *)0)->tst2 $3 = (int *) 0x4180 ------------testcase-------- diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 5059d09..7c6f7ac 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -586,7 +586,14 @@ struct arm_smmu_device { struct arm_smmu_strtab_cfg strtab_cfg; + int tst1; + + union { + u64 padding; u32 sync_count; + } __attribute__((aligned(8))); + + int tst2; /* IOMMU core code handle */ struct iommu_device iommu; > >> + } __attribute__((aligned(8))); >> >> /* IOMMU core code handle */ >> struct iommu_device iommu; >> > Thanks > > > > > . > -- Thanks! BestRegards