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Shutemov" , Davidlohr Bueso , Prakash Sangappa , James Houghton , Mina Almasry , Pasha Tatashin , Axel Rasmussen , Ray Fucillo , Andrew Morton , Mike Kravetz Subject: [PATCH] hugetlb: fix memory leak associated with vma_lock structure Date: Tue, 18 Oct 2022 16:36:01 -0700 Message-Id: <20221018233601.282381-1-mike.kravetz@oracle.com> X-Mailer: git-send-email 2.37.3 X-ClientProxiedBy: MW4PR04CA0299.namprd04.prod.outlook.com (2603:10b6:303:89::34) To BY5PR10MB4196.namprd10.prod.outlook.com (2603:10b6:a03:20d::23) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BY5PR10MB4196:EE_|MW4PR10MB6678:EE_ X-MS-Office365-Filtering-Correlation-Id: c95d5b7a-ad0f-49ee-ae84-08dab161866c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: P6YnhbRN7nQKOh9VtQLCMj0l0gTVA3cnJGGWh1CVXdeviozj/Zj4oUtgZjIPhsL+DzgrLznTzHKmvIjL2HzVS5NwsGx0NCMW9QtS/CNTKZSqgtpgN9xviXVfNzfM9PSEQzBxkWRegLgDuX2/Qz820LRCM3BwxzXy3eci5GmLdBrKuj/M8ud+uF1CESIefe1yDkr4SWVMsFfU5WH9EZFo94mVbUYzYf/HPnaIJMAuR6FRsdoGMNz4jE6U1U6RU24N5bHEnK2N66QmToKjGFTSxtMM4viAl2GGCN0jmtcjNBo6YDZubXvUs5dvMIZAF5sqzKrdE6vSEwSZKm/rsHAuW0quqsrNSCoHnp+hE/+nNTsido3CSZm88oSLh+544Q3ocGalkhGoXibfIZa/jeT2AsEMbAzVb8uGCphD3BSC8/6gBNCl3/ewIfzqCoC8b1lo4oAqQ++gzEv10Qf9q36MPVdp64L+l7PbWcnQmUlrr1DUhET4EwqTq4vuAad3q71L9vFgJxfOPDZzDXq4hKF/siB/ZEAwVVphT6QlLYw31nOUKg3MSKHSe4FjCVFbOprjkpA0XD1NT8ioEEzrVsRuCEgtU8X0zOAk9lTWS/A1nDeWhUYOjPcip0BLCyBt25m8z6EY1aZifJ6toNN6CGqfOhZGp4M9NFPjGjdua6mPfssP+ha+12tB90ZWhV1kXEJ1+FeKKiVOZqafbBnz1AizANnlIi1OBkeMmfoy/gVAsEo= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BY5PR10MB4196.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230022)(376002)(346002)(39860400002)(136003)(366004)(396003)(451199015)(66556008)(8676002)(6506007)(66476007)(4326008)(107886003)(6666004)(86362001)(2906002)(186003)(83380400001)(26005)(6512007)(8936002)(41300700001)(44832011)(2616005)(1076003)(7416002)(36756003)(5660300002)(66946007)(6486002)(966005)(478600001)(66899015)(54906003)(316002)(38100700002);DIR:OUT;SFP:1101; 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The structure is vma specific and can not be shared between vmas. At fork and various other times, vmas are duplicated via vm_area_dup(). When this happens, the pointer in the newly created vma must be cleared and the structure reallocated. Two hugetlb specific routines deal with this hugetlb_dup_vma_private and hugetlb_vm_op_open. Both routines are called for newly created vmas. hugetlb_dup_vma_private would always clear the pointer and hugetlb_vm_op_open would allocate the new vms_lock structure. This did not work in the case of this calling sequence pointed out in [1]. move_vma copy_vma new_vma = vm_area_dup(vma); new_vma->vm_ops->open(new_vma); --> new_vma has its own vma lock. is_vm_hugetlb_page(vma) clear_vma_resv_huge_pages hugetlb_dup_vma_private --> vma->vm_private_data is set to NULL When clearing hugetlb_dup_vma_private we actually leak the associated vma_lock structure. The vma_lock structure contains a pointer to the associated vma. This information can be used in hugetlb_dup_vma_private and hugetlb_vm_op_open to ensure we only clear the vm_private_data of newly created (copied) vmas. In such cases, the vma->vma_lock->vma field will not point to the vma. Update hugetlb_dup_vma_private and hugetlb_vm_op_open to not clear vm_private_data if vma->vma_lock->vma == vma. Also, log a warning if hugetlb_vm_op_open ever encounters the case where vma_lock has already been correctly allocated for the vma. [1] https://lore.kernel.org/linux-mm/5154292a-4c55-28cd-0935-82441e512fc3@huawei.com/ Fixes: 131a79b474e9 ("hugetlb: fix vma lock handling during split vma and range unmapping") Signed-off-by: Mike Kravetz --- mm/hugetlb.c | 31 ++++++++++++++++++++++++------- 1 file changed, 24 insertions(+), 7 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 02f781624fce..7f74cbff6619 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1014,15 +1014,23 @@ void hugetlb_dup_vma_private(struct vm_area_struct *vma) VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma); /* * Clear vm_private_data + * - For shared mappings this is a per-vma semaphore that may be + * allocated in a subsequent call to hugetlb_vm_op_open. + * Before clearing, make sure pointer is not associated with vma + * as this will leak the structure. This is the case when called + * via clear_vma_resv_huge_pages() and hugetlb_vm_op_open has already + * been called to allocate a new structure. * - For MAP_PRIVATE mappings, this is the reserve map which does * not apply to children. Faults generated by the children are * not guaranteed to succeed, even if read-only. - * - For shared mappings this is a per-vma semaphore that may be - * allocated in a subsequent call to hugetlb_vm_op_open. */ - vma->vm_private_data = (void *)0; - if (!(vma->vm_flags & VM_MAYSHARE)) - return; + if (vma->vm_flags & VM_MAYSHARE) { + struct hugetlb_vma_lock *vma_lock = vma->vm_private_data; + + if (vma_lock && vma_lock->vma != vma) + vma->vm_private_data = NULL; + } else + vma->vm_private_data = NULL; } /* @@ -4601,6 +4609,7 @@ static void hugetlb_vm_op_open(struct vm_area_struct *vma) struct resv_map *resv = vma_resv_map(vma); /* + * HPAGE_RESV_OWNER indicates a private mapping. * This new VMA should share its siblings reservation map if present. * The VMA will only ever have a valid reservation map pointer where * it is being copied for another still existing VMA. As that VMA @@ -4616,10 +4625,18 @@ static void hugetlb_vm_op_open(struct vm_area_struct *vma) /* * vma_lock structure for sharable mappings is vma specific. * Clear old pointer (if copied via vm_area_dup) and create new. + * Before clearing, make sure vma_lock is not for this vma. */ if (vma->vm_flags & VM_MAYSHARE) { - vma->vm_private_data = NULL; - hugetlb_vma_lock_alloc(vma); + struct hugetlb_vma_lock *vma_lock = vma->vm_private_data; + + if (vma_lock) { + if (vma_lock->vma != vma) { + vma->vm_private_data = NULL; + hugetlb_vma_lock_alloc(vma); + } else + pr_warn("HugeTLB: vma_lock already exists in %s.\n", __func__); + } } }