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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id b14-20020a170902650e00b00186b6bb2f48sm2022328plk.129.2022.11.17.16.31.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Nov 2022 16:31:25 -0800 (PST) Date: Thu, 17 Nov 2022 16:31:24 -0800 From: Kees Cook To: Linus Torvalds Cc: David Hildenbrand , linux-kernel@vger.kernel.org, x86@kernel.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-perf-users@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Morton , Jason Gunthorpe , John Hubbard , Peter Xu , Greg Kroah-Hartman , Andrea Arcangeli , Hugh Dickins , Nadav Amit , Vlastimil Babka , Matthew Wilcox , Mike Kravetz , Muchun Song , Shuah Khan , Lucas Stach , David Airlie , Oded Gabbay , Arnd Bergmann , Christoph Hellwig , Alex Williamson , Oleg Nesterov , Richard Henderson , Ivan Kokshaysky , Matt Turner , Catalin Marinas , Will Deacon , Thomas Bogendoerfer , Michael Ellerman , Nicholas Piggin , Christophe Leroy , "David S. Miller" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Richard Weinberger , Anton Ivanov , Johannes Berg , Eric Biederman , Alexander Viro , Peter Zijlstra , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Kentaro Takeda , Tetsuo Handa , Paul Moore , James Morris , "Serge E. Hallyn" Subject: Re: [PATCH mm-unstable v1 20/20] mm: rename FOLL_FORCE to FOLL_PTRACE Message-ID: <202211171630.8EABF5EDD@keescook> References: <20221116102659.70287-1-david@redhat.com> <20221116102659.70287-21-david@redhat.com> <202211171439.CDE720EAD@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org On Thu, Nov 17, 2022 at 03:20:01PM -0800, Linus Torvalds wrote: > On Thu, Nov 17, 2022 at 2:58 PM Kees Cook wrote: > > > > Oh, er, why does get_arg_page() even need FOLL_FORCE? This is writing the > > new stack contents to the nascent brpm->vma, which was newly allocated > > with VM_STACK_FLAGS, which an arch can override, but they all appear to include > > VM_WRITE | VM_MAYWRITE. > > Yeah, it does seem entirely superfluous. > > It's been there since the very beginning (although in that original > commit b6a2fea39318 it was there as a '1' to the 'force' argument to > get_user_pages()). > > I *think* it can be just removed. But as long as it exists, it should > most definitely not be renamed to FOLL_PTRACE. > > There's a slight worry that it currently hides some other setup issue > that makes it matter, since it's been that way so long, but I can't > see what it is. My test system boots happily with it removed. I'll throw it into -next and see if anything melts... -- Kees Cook