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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id u127sm3234989pfb.180.2021.02.10.11.35.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Feb 2021 11:35:02 -0800 (PST) Date: Wed, 10 Feb 2021 11:35:01 -0800 From: Kees Cook To: Yu-cheng Yu Cc: x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu , haitao.huang@intel.com, Christoph Hellwig Subject: Re: [PATCH v20 07/25] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Message-ID: <202102101134.72F7495@keescook> References: <20210210175703.12492-1-yu-cheng.yu@intel.com> <20210210175703.12492-8-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210210175703.12492-8-yu-cheng.yu@intel.com> X-Stat-Signature: uo1jgirnemuy3sdz5ax3y611bqy8bur5 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: CE9F8130 Received-SPF: none (chromium.org>: No applicable sender policy available) receiver=imf12; identity=mailfrom; envelope-from=""; helo=mail-pf1-f176.google.com; client-ip=209.85.210.176 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1612985702-982160 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 Wed, Feb 10, 2021 at 09:56:45AM -0800, Yu-cheng Yu wrote: > The x86 family of processors do not directly create read-only and Dirty > PTEs. These PTEs are created by software. One such case is that kernel > read-only pages are historically setup as Dirty. > > New processors that support Shadow Stack regard read-only and Dirty PTEs as > shadow stack pages. This results in ambiguity between shadow stack and > kernel read-only pages. To resolve this, removed Dirty from kernel read- > only pages. > > Signed-off-by: Yu-cheng Yu Reviewed-by: Kees Cook -- Kees Cook