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Thu, 11 Apr 2024 10:18:59 +0800 Subject: Re: [PATCH] fork: defer linking file vma until vma is fully initialized To: Andrew Morton CC: , , , , , , , , , , , , , , References: <20240410091441.3539905-1-linmiaohe@huawei.com> <20240410132157.b0e54f59b066f2c1d322d425@linux-foundation.org> From: Miaohe Lin Message-ID: Date: Thu, 11 Apr 2024 10:18:58 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20240410132157.b0e54f59b066f2c1d322d425@linux-foundation.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.173.135.154] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 64F45140016 X-Stat-Signature: 9faaasha63sj8yt7hz9dexd86gcq1q4z X-HE-Tag: 1712801944-182450 X-HE-Meta: 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 QAmx0fw5 IO34VOiVTOdWz6d00/PG0DAHtKNEcP7nxhj1wE+2zhw1KX4rRAp1jkDlV/NU+rjV0Z9l1OX/9Z/MGPkxTk1e9zakmXKXA+yzxrLYQID/TEccqKF4MLLjKMPGxu8yaF0GpTTW5cnBf1Gn+c6kwdYLsiWpQAw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.003248, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024/4/11 4:21, Andrew Morton wrote: > On Wed, 10 Apr 2024 17:14:41 +0800 Miaohe Lin wrote: > >> Thorvald reported a WARNING [1]. And the root cause is below race: >> >> CPU 1 CPU 2 >> fork hugetlbfs_fallocate >> dup_mmap hugetlbfs_punch_hole >> i_mmap_lock_write(mapping); >> vma_interval_tree_insert_after -- Child vma is visible through i_mmap tree. >> i_mmap_unlock_write(mapping); >> hugetlb_dup_vma_private -- Clear vma_lock outside i_mmap_rwsem! >> i_mmap_lock_write(mapping); >> hugetlb_vmdelete_list >> vma_interval_tree_foreach >> hugetlb_vma_trylock_write -- Vma_lock is cleared. >> tmp->vm_ops->open -- Alloc new vma_lock outside i_mmap_rwsem! >> hugetlb_vma_unlock_write -- Vma_lock is assigned!!! >> i_mmap_unlock_write(mapping); >> >> hugetlb_dup_vma_private() and hugetlb_vm_op_open() are called outside >> i_mmap_rwsem lock while vma lock can be used in the same time. Fix this >> by deferring linking file vma until vma is fully initialized. Those vmas >> should be initialized first before they can be used. > > Cool. I queued this in mm-hotfixes (for 6.8-rcX) and I added a cc:stable. Thanks for doing this. And any comment or thought would be really welcome and appreciated. . > . >