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[2a02:3100:a017:2b01:5fe:203b:7cd2:a640]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49fc7cba562sm86917495e9.2.2026.09.19.02.07.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 02:07:50 -0700 (PDT) Date: Sat, 19 Sep 2026 11:07:48 +0200 From: Karl Mehltretter To: Harry Yoo Cc: Vlastimil Babka , Andrew Morton , Rasmus Villemoes , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Catalin Marinas , Kees Cook , "Gustavo A . R . Silva" , Arnd Bergmann , Greg Kroah-Hartman , Shuah Khan , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-hardening@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH v3 0/5] slab: ZERO_SIZE_PTR alignment and ERR_PTR hardening Message-ID: References: <20260903203720.63689-1-kmehltretter@gmail.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Sep 04, 2026 at 12:25:59PM +0100, Harry Yoo wrote: > I don't understand why v3 of this patchset suddenly implements > hardening for kfree() and usercopy to handle ERR_PTR(). > > The address range for 'zero or NULL PTR' range and ERR_PTR() do not > overlap. The bugfixes and hardening patches are irrelevant. > It should be a separate series? > > Also usercopy.c changes go through the hardening tree, slub.c and > slub_kunit.c changes go through the slab tree, and LKDTM has its own > tree. Patch 3 and 5 touch files across multiple trees, which can be > avoided. > I added the ERR_PTR changes after Kees raised handling that range in the v2 review [1]. The two topics also came up together in the 2014 [2] and 2019 [3] discussions; in the latter, Jann suggested a separate warning-and-return check [4]. I wanted to broaden the discussion and see whether considering both together might suggest a better approach. I agree that the resulting implementations are independent. I'll send v4 with the ZERO_SIZE_PTR alignment, exact-match and zero-size KUnit patches only, and pursue the ERR_PTR work separately. I'll split that work along the SLUB, usercopy and LKDTM boundaries you pointed out. [1] https://lore.kernel.org/r/202608111716.0FA9DB17@keescook/ [2] https://lore.kernel.org/r/87oaumdz1f.fsf@rasmusvillemoes.dk/ [3] https://lore.kernel.org/r/20191010103151.7708-1-mayhs11saini@gmail.com/ [4] https://lore.kernel.org/r/CAG48ez05QVn6_gQ2TBrRa1a_DWQoaSSYubUsu5YMWxx-gqMijQ@mail.gmail.com/ Thanks, Karl