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[2a02:3100:a017:2b01:5fe:203b:7cd2:a640]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49fc6ca43edsm124495965e9.0.2026.09.19.02.39.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 02:39:50 -0700 (PDT) Date: Sat, 19 Sep 2026 11:39:47 +0200 From: Karl Mehltretter To: "Vlastimil Babka (SUSE)" Cc: Harry Yoo , 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 3/5] slab: handle ERR_PTR values in kfree and hardened usercopy Message-ID: References: <20260903203720.63689-1-kmehltretter@gmail.com> <20260903203720.63689-4-kmehltretter@gmail.com> <497a85d3-e062-4930-bcb8-c86a8205e7b2@kernel.org> 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: <497a85d3-e062-4930-bcb8-c86a8205e7b2@kernel.org> > > + if (WARN_ON(IS_ERR(object))) > > Wonder if WARN_ON_ONCE() would be better. > Also wonder about the benefits for hardening (as opposed to debugging). > Without this check it would fault. Now it warns, but hardened setups often > use panic_on_warn anyway, so the result is the same? > Yes, I'll switch to WARN_ON_ONCE(). You're right about panic_on_warn. The benefit is a clearer diagnostic and, when warnings aren't fatal, returning before virt_to_page(). I'll split out the ERR_PTR patches as Harry suggested and recheck the KUnit warning-count test with WARN_ON_ONCE(). Thanks, Karl