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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 5632C1C0007 X-Stat-Signature: 8qcziuux6kzuc8385a94n96thuo3k8x1 X-HE-Tag: 1789808873-276918 X-HE-Meta: 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 NAQaL10E 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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