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Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH V1] iommu/sva: Fix crash in iommu_sva_unbind_device() Content-Language: en-US To: Yi Liu , , , CC: , , , References: <20260224183056.2628698-1-lizhi.hou@amd.com> <1c486a5a-7115-44fc-9705-18b292cb9d00@intel.com> From: Lizhi Hou In-Reply-To: <1c486a5a-7115-44fc-9705-18b292cb9d00@intel.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF00002322:EE_|BL1PR12MB5970:EE_ X-MS-Office365-Filtering-Correlation-Id: 4f5039b4-c55f-45f4-c0d3-08de74ba8f20 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|82310400026|36860700013|376014|7053199007|13003099007; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb08.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(82310400026)(36860700013)(376014)(7053199007)(13003099007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: NId5jVyKml+x+AeXK8d4jjthKft+0lC8X/6+2MD7JD4tKH2nwguJu8Qqr1y461ee25VCRPrnXrAp0QL3/rCuFIsHd6pWuYsaCaAlV0fSWJwyYcKvPv1jNn3YhZw4ltSQu4b5aWaabkyjcvJZHILNRsDgd1A5d0Yg6Pba3UQ2/m1yLYji+YMtmGBEqmMBwxqUhsMnS2ucNXEfWf98EDW6MN/mQsh6umXqI+2ZLsH7cy+9ar3ldcK+EIp/wQPwY/cszy6o7sXB12eH+6fFMdDE42R4J3xviAhwZrSw6vyarw3/EdDDrznupREBOrITGy5QgFSB62ESCKGGI8GKCawoScOsLPKV4ia0YRgr8qBq2WTEgwtFupCZ2O+QE8nu2eX4Ky+Sw7Uc/uL5K4avngSgg/h6kt0pB4rsFScrpcf6yDdBeM/RPkNfrb3XyQQ7aOI6 X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Feb 2026 22:09:34.6392 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4f5039b4-c55f-45f4-c0d3-08de74ba8f20 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SJ1PEPF00002322.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5970 On 2/25/26 01:35, Yi Liu wrote: > [You don't often get email from yi.l.liu@intel.com. Learn why this is > important at https://aka.ms/LearnAboutSenderIdentification ] > > On 2026/2/25 02:30, Lizhi Hou wrote: >> domain->mm->iommu_mm can be freed by iommu_domain_free(): >>    iommu_domain_free() >>      mmdrop() >>        __mmdrop() >>          mm_pasid_drop() >> After iommu_domain_free() returns, accessing domain->mm->iommu_mm may >> dereference a freed mm structure, leading to a crash. >> >> Fix this by taking a reference to the mm via mmgrab() before >> calling iommu_domain_free(), and dropping it with mmdrop() after >> finishing access to domain->mm->iommu_mm. > > need to be more accurate. The issue is that iommu_mm is freed in > mm_pasid_drop(), so after iommu_domain_free(), the later access to > iommu_mm is problematic. The description mentioned this. After iommu_domain_free() returns, accessing domain->mm->iommu_mm may dereference a freed mm structure, leading to a crash. > >> Fixes: e37d5a2d60a3 ("iommu/sva: invalidate stale IOTLB entries for >> kernel address space") >> Signed-off-by: Lizhi Hou >> --- >>   drivers/iommu/iommu-sva.c | 2 ++ >>   1 file changed, 2 insertions(+) >> >> diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c >> index 07d64908a05f..523b8c65c86f 100644 >> --- a/drivers/iommu/iommu-sva.c >> +++ b/drivers/iommu/iommu-sva.c >> @@ -179,6 +179,7 @@ void iommu_sva_unbind_device(struct iommu_sva >> *handle) >>               return; >>       } >> >> +     mmgrab(domain->mm); >>       iommu_detach_device_pasid(domain, dev, iommu_mm->pasid); >>       if (--domain->users == 0) { >>               list_del(&domain->next); >> @@ -190,6 +191,7 @@ void iommu_sva_unbind_device(struct iommu_sva >> *handle) >>               if (list_empty(&iommu_sva_mms)) >>                       iommu_sva_present = false; >>       } >> +     mmdrop(domain->mm); >> >>       mutex_unlock(&iommu_sva_lock); >>       kfree(handle); > > will moving the below hunk in front of iommu_domain_free() simpler? > Only when (--domain->users == 0), shall the code check if sva_domains > is empty. right? I am not sure if this can be moved in front of iommu_domain_free(). Will iommu_domain_free() be possible to impact sva_domains? iommu_domain_free() calls domain->ops->free(). Could this call back free sva_domain? Lizhi > >         if (list_empty(&iommu_mm->sva_domains)) { >             list_del(&iommu_mm->mm_list_elm); >             if (list_empty(&iommu_sva_mms)) >                 iommu_sva_present = false; >         } > > Regards, > Yi Liu