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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id n9sm205492pjq.38.2021.03.15.10.28.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Mar 2021 10:28:24 -0700 (PDT) Date: Mon, 15 Mar 2021 10:28:23 -0700 From: Kees Cook To: Andrew Morton Cc: Thomas Gleixner , stable@vger.kernel.org, Elena Reshetova , x86@kernel.org, Andy Lutomirski , Peter Zijlstra , Catalin Marinas , Will Deacon , Mark Rutland , Alexander Potapenko , Alexander Popov , Ard Biesheuvel , Jann Horn , kernel-hardening@lists.openwall.com, linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka , David Hildenbrand , Mike Rapoport , Jonathan Corbet , Randy Dunlap Subject: Re: [PATCH v5 1/7] mm: Restore init_on_* static branch defaults Message-ID: <202103151027.88B63D0@keescook> References: <20210309214301.678739-1-keescook@chromium.org> <20210309214301.678739-2-keescook@chromium.org> <20210310155602.e005171dbecbc0be442f8aad@linux-foundation.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210310155602.e005171dbecbc0be442f8aad@linux-foundation.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210315_172827_671169_A675684D X-CRM114-Status: GOOD ( 15.63 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Mar 10, 2021 at 03:56:02PM -0800, Andrew Morton wrote: > On Tue, 9 Mar 2021 13:42:55 -0800 Kees Cook wrote: > > > Choosing the initial state of static branches changes the assembly layout > > (if the condition is expected to be likely, inline, or unlikely, out of > > line via a jump). The _TRUE/_FALSE defines for CONFIG_INIT_ON_*_DEFAULT_ON > > were accidentally removed. These need to stay so that the CONFIG controls > > the pessimization of the resulting static branch NOP/JMP locations. > > Changelog doesn't really explain why anyone would want to apply this > patch. This is especially important for -stable patches. > > IOW, what is the user visible effect of the bug? Yeah, that's a good point, and in writing more details I decided this wasn't actually worth a stable patch, and should just get folded into later patches. Thanks for the sanity-check! -- Kees Cook _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel