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Fri, 9 Apr 2021 14:49:10 +0800 (HKT) Received: from alex-virtual-machine (172.16.253.254) by KSBJMAIL4.kingsoft.cn (10.88.1.79) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Fri, 9 Apr 2021 14:49:10 +0800 Date: Fri, 9 Apr 2021 14:49:09 +0800 From: Aili Yao To: "Luck, Tony" CC: Borislav Petkov , "x86@kernel.org" , "linux-mm@kvack.org" , Andy Lutomirski , "HORIGUCHI NAOYA( =?UTF-8?B?5aCA5Y+j44CA55u05Lmf?=)" , Subject: Re: [RFC 0/4] Fix machine check recovery for copy_from_user Message-ID: <20210409144909.3488db39@alex-virtual-machine> In-Reply-To: <595ed0ac4fbb470ca9cfd256aaf1810e@intel.com> References: <20210326000235.370514-1-tony.luck@intel.com> <20210408101335.28fd3692@alex-virtual-machine> <595ed0ac4fbb470ca9cfd256aaf1810e@intel.com> Organization: kingsoft X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [172.16.253.254] X-ClientProxiedBy: KSBJMAIL1.kingsoft.cn (10.88.1.31) To KSBJMAIL4.kingsoft.cn (10.88.1.79) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrDLMWRmVeSWpSXmKPExsXCFcHor/vsR36CwYEJ6hafN/xjs7i35j+r xflda1ktLjYeYLR4c+Eei8WPDY9ZHdg8vrf2sXgs3vOSyWPTqk42j02fJrF7vLi6kSWANYrL JiU1J7MstUjfLoEro+/3UraCuRwVB3dJNTDuYOti5OSQEDCROPRlI2MXIxeHkMB0JonHbb+Z IJyXjBJn/txi7WLk4GARUJHY8YwFpIFNQFVi171ZrCC2iICaxKXFD5hB6pkFGpkkDn1+CpYQ FnCR+NA0F2wDr4CVxM1VN5hAbE4BS4mnSzrAaoQEZjJKLDgqAmLzC4hJ9F75zwSyS0LAXuLx ekWIVkGJkzOfgO1lFtCROLHqGDOELS+x/e0cZogxihKHl/xih3hGSeJI9wyox2Ilmg7cYpvA KDwLyahZSEbNQjJqASPzKkaW4tx0w02MkAgI38E4r+mj3iFGJg7GQ4wSHMxKIrzNzfkJQrwp iZVVqUX58UWlOanFhxilOViUxHkXf8lLEBJITyxJzU5NLUgtgskycXBKNTBJT9pat1Vr96xd R3scc9Zv9nTr3sqq+Ojam3v73bbfUl9zfX9f8EzfmXs3uat76ee+n6mgIbPPkXN24Nmt8rcO 3L8je+ycnvzPb976iwt28W85ktljaJT8N4P91FSb+Iff3ZaFfU1WLA0+uqD/1PzOKyHGsT7M X6L4Tt79qcR06EDzuo+T2L/Guez3uVK6eMNOd7t7Omfz20/sN2JZatRwqzteK+/agSnC7zkW rPP5y/n+9Yvm3XWPNiV+m+0ZHfDNfGJjZdTEGYZnJi61TJxevvSkiEj94Z6VLdaRcunSa+Q7 sls62kIsZv7K2PO/uibqwKOuFkUZo+vmc8X993ucjmhhXH30WNQskUbGnPglSizFGYmGWsxF xYkAaD/xBu8CAAA= X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 00B82A000391 X-Stat-Signature: wniaxretdt9989uqahqh9e549ytjmsps Received-SPF: none (kingsoft.com>: No applicable sender policy available) receiver=imf24; identity=mailfrom; envelope-from=""; helo=mail.kingsoft.com; client-ip=114.255.44.145 X-HE-DKIM-Result: none/none X-HE-Tag: 1617950952-179240 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000009, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 8 Apr 2021 14:39:09 +0000 "Luck, Tony" wrote: > > I have one scenario, may you take into account: > > > > If one copyin case occurs, write() returned by your patch, the user process may > > check the return values, for errors, it may exit the process, then the error page > > will be freed, and then the page maybe alloced to other process or to kernel itself, > > then code will initialize it and this will trigger one SRAO, if it's used by kernel, > > we may do nothing for this, and kernel may still touch it, and lead to one panic. > > In this case kill_me_never() calls memory_failure() with flags == 0. I think (hope!) > that means that it will unmap the page from the task, but will not send a signal. > > When the task exits the PTE for this page has the swap/poison signature, so the > page is not freed for re-use. > > -Tony Oh, Yes, Sorry for my rudeness and error-understandings, I just happen to can't control my emotions and get confused for some other things. Thanks! Aili Yao