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Mon, 3 May 2021 20:53:05 +0000 Subject: Re: [PATCH 2/2] mm/hugetlb: Fix cow where page writtable in child To: Peter Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Hugh Dickins , Andrew Morton , Andrea Arcangeli , Axel Rasmussen References: <20210501144110.8784-1-peterx@redhat.com> <20210501144110.8784-3-peterx@redhat.com> From: Mike Kravetz Message-ID: Date: Mon, 3 May 2021 13:53:03 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 In-Reply-To: <20210501144110.8784-3-peterx@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [50.38.35.18] X-ClientProxiedBy: MWHPR13CA0034.namprd13.prod.outlook.com (2603:10b6:300:95::20) To BY5PR10MB4196.namprd10.prod.outlook.com (2603:10b6:a03:20d::23) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.2.112] (50.38.35.18) by MWHPR13CA0034.namprd13.prod.outlook.com (2603:10b6:300:95::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4108.10 via Frontend Transport; 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dkim=pass header.d=oracle.com header.s=corp-2020-01-29 header.b=VRSy02qg; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=pX2IzOAp; spf=none (imf05.hostedemail.com: domain of mike.kravetz@oracle.com has no SPF policy when checking 156.151.31.86) smtp.mailfrom=mike.kravetz@oracle.com; dmarc=pass (policy=none) header.from=oracle.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 281FBE000111 X-Stat-Signature: y4c3744j51owjwa6wt53h6m31au4ucim Received-SPF: none (oracle.com>: No applicable sender policy available) receiver=imf05; identity=mailfrom; envelope-from=""; helo=userp2130.oracle.com; client-ip=156.151.31.86 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620075188-561808 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 5/1/21 7:41 AM, Peter Xu wrote: > When fork() and copy hugetlb page range, we'll remember to wrprotect src pte if > needed, however we forget about the child! Without it, the child will be able > to write to parent's pages when mapped as PROT_READ|PROT_WRITE and MAP_PRIVATE, > which will cause data corruption in the parent process. > > This issue can also be exposed by "memfd_test hugetlbfs" kselftest (if it can > pass the F_SEAL_FUTURE_WRITE test first, though). > > Signed-off-by: Peter Xu > --- > mm/hugetlb.c | 2 ++ > 1 file changed, 2 insertions(+) Reviewed-by: Mike Kravetz I think we need to add, "Fixes: 4eae4efa2c29" as this is now in v5.12 -- Mike Kravetz