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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id v62-20020a626141000000b0054097cb2da6sm7726006pfb.38.2022.10.03.11.39.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Oct 2022 11:39:11 -0700 (PDT) Date: Mon, 3 Oct 2022 11:39:10 -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 Subject: Re: [PATCH v2 22/39] mm: Don't allow write GUPs to shadow stack memory Message-ID: <202210031134.B0B6B37@keescook> References: <20220929222936.14584-1-rick.p.edgecombe@intel.com> <20220929222936.14584-23-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220929222936.14584-23-rick.p.edgecombe@intel.com> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1664822353; 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=G7bUMV+FEZy7kwIPvofvWVHEzM2JjGpJ/T9cn7FANKI=; b=H4u6Spl/zufsElLv1jR6AGOM+yBwqhhDTDIcTeysIWC1xYtcvNOx2cwHRwP3WrDFxa+YJ8 5BoF8TrsGiDc9WRNvLELHnJp/ytq4HJmInW8pU03feYFaqkSVpJOMN4dsWSHSUyRXtkvQO rSYJM/jWLa3rgN4sKDIbqhqFfzsQacY= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=DbL7LAsM; spf=pass (imf02.hostedemail.com: domain of keescook@chromium.org designates 209.85.215.177 as permitted sender) smtp.mailfrom=keescook@chromium.org; dmarc=pass (policy=none) header.from=chromium.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1664822353; a=rsa-sha256; cv=none; b=Yiyvyzmv1BiER5mPVp5uqRJECRBg0+A+ancde8vvsOjbOZjUZYQYAGlAeCVq53Jw+gTsvk qqvJSQG9Q0D5IrI4ZvC2sQ92yWYPQtFOII4CTrgKtu4vmCDLmy0aBQKaDkFhzb8E9O78kR /6FGlS8u6urBnPVl+yHF3X5pdfCOVpc= X-Rspam-User: Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=DbL7LAsM; spf=pass (imf02.hostedemail.com: domain of keescook@chromium.org designates 209.85.215.177 as permitted sender) smtp.mailfrom=keescook@chromium.org; dmarc=pass (policy=none) header.from=chromium.org X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: DF26080011 X-Stat-Signature: byef7zffka7r41ek8f5wfhb57exar8r3 X-HE-Tag: 1664822352-521954 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 03:29:19PM -0700, Rick Edgecombe wrote: > [...] > Still allow FOLL_FORCE to write through shadow stack protections, as it > does for read-only protections. As I asked in the cover letter: why do we need to add this for shstk? It was a mistake for general memory. :P > [...] > diff --git a/mm/gup.c b/mm/gup.c > index 5abdaf487460..56da98f3335c 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1043,7 +1043,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) > return -EFAULT; > > if (write) { > - if (!(vm_flags & VM_WRITE)) { > + if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) { > if (!(gup_flags & FOLL_FORCE)) > return -EFAULT; > /* How about this instead: return -EFAULT; if (write) { + if (vm_flags & VM_SHADOW_STACK) + return -EFAULT; if (!(vm_flags & VM_WRITE)) { if (!(gup_flags & FOLL_FORCE)) return -EFAULT; -- Kees Cook