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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id h4-20020a170902f54400b0017ee7f331ffsm3242061plf.291.2022.10.03.11.22.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Oct 2022 11:22:53 -0700 (PDT) Date: Mon, 3 Oct 2022 11:22:52 -0700 From: Kees Cook To: Rick Edgecombe 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" , Weijiang Yang , "Kirill A . Shutemov" , joao.moreira@intel.com, John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, Yu-cheng Yu Subject: Re: [PATCH v2 16/39] x86/mm: Update maybe_mkwrite() for shadow stack Message-ID: <202210031122.A27CE24D39@keescook> References: <20220929222936.14584-1-rick.p.edgecombe@intel.com> <20220929222936.14584-17-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220929222936.14584-17-rick.p.edgecombe@intel.com> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1664821375; a=rsa-sha256; cv=none; b=Kd6Gt248MvO6fDQylkGDJ8lI1qFg6Odj8dY5Kz3Pe6aflhFsrqQ4OtvyaOobsSOQh0ydjh Kuh4ZqrdnJUDHxqo4gQv9eEu7x2Ex4iJ/TYAjfn5C5Bmq3mrtqEqmKehIIF+a3SD0NACuZ rDZNCjPV9oBovU62QtygSr9LteWLIm4= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=bKitYN0y; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf27.hostedemail.com: domain of keescook@chromium.org designates 209.85.210.178 as permitted sender) smtp.mailfrom=keescook@chromium.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1664821375; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=DpamCQg4r6DJ9TEvfJUx5RfmiJZUBbQ1vJaFAYMtbtE=; b=JfvpkPD68bQiQZvHPru7vEU4TIupY5//A0rgtuiaNWZzOfWTVqxr66DPY9oC+7VoJmQjDt D2+ZAYfhqtN+ACz6SDUs1yaIU7L2eb3s3KrYt0SxsgcElI0+z4o7M1C3XA/4mXgCVVDlrh +EKAzvJHOnkCv9v+1A3wWhnRLRaPTbs= X-Rspam-User: Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=bKitYN0y; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf27.hostedemail.com: domain of keescook@chromium.org designates 209.85.210.178 as permitted sender) smtp.mailfrom=keescook@chromium.org X-Stat-Signature: 1agg7z8bowiscp63cnrje339wi85qmbg X-Rspamd-Queue-Id: 2FFBE4000F X-Rspamd-Server: rspam09 X-HE-Tag: 1664821374-819146 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 Thu, Sep 29, 2022 at 03:29:13PM -0700, Rick Edgecombe wrote: > From: Yu-cheng Yu > > When serving a page fault, maybe_mkwrite() makes a PTE writable if there is > a write access to it, and its vma has VM_WRITE. Shadow stack accesses to > shadow stack vma's are also treated as write accesses by the fault handler. > This is because setting shadow stack memory makes it writable via some > instructions, so COW has to happen even for shadow stack reads. > > So maybe_mkwrite() should continue to set VM_WRITE vma's as normally > writable, but also set VM_WRITE|VM_SHADOW_STACK vma's as shadow stack. > > Do this by adding a pte_mkwrite_shstk() and a cross-arch stub. Check for > VM_SHADOW_STACK in maybe_mkwrite() and call pte_mkwrite_shstk() > accordingly. > > Apply the same changes to maybe_pmd_mkwrite(). > > Signed-off-by: Yu-cheng Yu Reviewed-by: Kees Cook -- Kees Cook