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Fri, 20 Aug 2021 21:51:52 -0700 (PDT) MIME-Version: 1.0 References: <20210706190620.1290391-1-tony.luck@intel.com> <20210818002942.1607544-1-tony.luck@intel.com> <20210818002942.1607544-2-tony.luck@intel.com> <20210820185945.GA1623421@agluck-desk2.amr.corp.intel.com> <20210820202346.GA1623796@agluck-desk2.amr.corp.intel.com> In-Reply-To: <20210820202346.GA1623796@agluck-desk2.amr.corp.intel.com> From: Tony Luck Date: Fri, 20 Aug 2021 21:51:41 -0700 Message-ID: Subject: Re: [PATCH v2 1/3] x86/mce: Avoid infinite loop for copy from user recovery To: Borislav Petkov Cc: Jue Wang , Ding Hui , =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Oscar Salvador , Youquan Song , huangcun@sangfor.com.cn, X86-ML , Linux Edac Mailing List , Linux-MM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=intel-com.20150623.gappssmtp.com header.s=20150623 header.b=MpeK7YtJ; spf=pass (imf03.hostedemail.com: domain of tonyluck@gmail.com designates 209.85.210.170 as permitted sender) smtp.mailfrom=tonyluck@gmail.com; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=intel.com (policy=none) X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: D75C1300009B X-Stat-Signature: uptz8yhj3jki3635qjzeqoj6fdjkzrk4 X-HE-Tag: 1629521513-982128 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000397, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Aug 20, 2021 at 1:25 PM Luck, Tony wrote: > Probably the same for the two different addresses case ... though I'm > not 100% confident about that. There could be some ioctl() that peeks > at two parts of a passed in structure, and the user might pass in a > structure that spans across a page boundary with both pages poisoned. > But that would only hit if the driver code ignored the failure of the > first get_user() and blindly tried the second. So I'd count that as a > critically bad driver bug. Or maybe driver writers are just evil :-( for (i = 0; i < len; i++) { tx_wait(10); get_user(dsp56k_host_interface.data.b[1], bin++); get_user(dsp56k_host_interface.data.b[2], bin++); get_user(dsp56k_host_interface.data.b[3], bin++); } -Tony