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Thu, 10 Sep 2026 10:46:47 +0800 (CST) Received: from kwepemr500001.china.huawei.com (unknown [7.202.194.229]) by mail.maildlp.com (Postfix) with ESMTPS id A874640561; Thu, 10 Sep 2026 10:57:59 +0800 (CST) Received: from [10.174.178.9] (10.174.178.9) by kwepemr500001.china.huawei.com (7.202.194.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Thu, 10 Sep 2026 10:57:58 +0800 Message-ID: Date: Thu, 10 Sep 2026 10:57:57 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/rmap: fix missing barrier between anon_vma init and vma->anon_vma publish To: Jann Horn CC: , , , , , , , , , , , , , References: <20260908122924.554373-1-tujinjiang@huawei.com> From: Jinjiang Tu In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.9] X-ClientProxiedBy: kwepems500001.china.huawei.com (7.221.188.70) To kwepemr500001.china.huawei.com (7.202.194.229) X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 1EC0B1C0006 X-Stat-Signature: 6bdbhdxgi85kiu3pxb849b3o5rrnoiww X-Rspam-User: X-HE-Tag: 1789009089-446016 X-HE-Meta: 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 Is4V+ZsC 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2026/9/9 23:25, Jann Horn 写道: > On Tue, Sep 8, 2026 at 2:57 PM Jinjiang Tu wrote: >> diff --git a/mm/rmap.c b/mm/rmap.c >> index d1819fd69938..f3b21aaa34ee 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -209,7 +209,11 @@ int __anon_vma_prepare(struct vm_area_struct *vma) >> /* page_table_lock to protect against threads */ >> spin_lock(&mm->page_table_lock); >> if (likely(!vma->anon_vma)) { >> - vma->anon_vma = anon_vma; >> + /* >> + * Make anon_vma fields visible before anon_vma is published. >> + * Paired with an address dependency in reusable_anon_vma(). >> + */ >> + smp_store_release(&vma->anon_vma, anon_vma); > Yes, this should go in. There are remaining theoretical issues (we > really should also be using READ_ONCE() in places like unuse_mm(), see > ), > but this is the important fix. Theoretically yes, but I'm curious whether these are actual problems in practice. In hugepage_vma_revalidate() and unuse_mm(), the code only checks whether anon_vma is non-NULL — it doesn't dereference anon_vma to access its fields. In KSM, rmap_item->anon_vma is assigned from vma->anon_vma, and the rmap_item is then inserted into a stable node. There is a very long time window before rmap_walk_ksm() could ever observe it. >