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b=G93U9dw3WdFE1Gz1DHEVRE8oFj43IggB+4gmxCTsEnDIw6l1YYubgBjhMYe5X0035 3ORwfo6AyHOb3zauNwZCrU5QtDlaBRgotCKTGdPna6HLqcX69OpWMGY0UjFB4vbCWY JfxH8Qn+6ZVNdZqwElhZuI+2c6U2xDbcwLvthUcI= Date: Wed, 10 Apr 2024 13:21:57 -0700 From: Andrew Morton To: Miaohe Lin Cc: , , , , , , , , , , , , , , Subject: Re: [PATCH] fork: defer linking file vma until vma is fully initialized Message-Id: <20240410132157.b0e54f59b066f2c1d322d425@linux-foundation.org> In-Reply-To: <20240410091441.3539905-1-linmiaohe@huawei.com> References: <20240410091441.3539905-1-linmiaohe@huawei.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 51DD21C000A X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: utf6uif4jxyqsr3aem6wmmzwk6wfrhu8 X-HE-Tag: 1712780521-650025 X-HE-Meta: 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 XIGBxEQv xHC8yIMvHKy7Ramgsk1QdHYNpwcdo5BHTLVocqAOkIsCQzY23YgK5YvwHeliN29KbivGI/n33ebx1M5GH+AJ0EgtYlAkdBX1ClBfBF8p6IyBGm6p096ufjx7KKrFyw7VoVMKh8vmxeqLQkzt7burlEeCj0ZSmN6TWd2a9VUTa8ctT97DuDwuRahQvqwOb706LL4KB1OjugX4DgP0WvrCZvaxbFyQ9JgnzGo03gKvHPbEoN2Unu/5AIjmuqfQyRfx2Ta9y X-Bogosity: Ham, tests=bogofilter, spamicity=0.002970, 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 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.