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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <497a85d3-e062-4930-bcb8-c86a8205e7b2@kernel.org> X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: 8qg1eq9wmqbfmte3af5ue338stwd4t8r X-Rspamd-Queue-Id: 73509A000A X-HE-Tag: 1789810792-864703 X-HE-Meta: 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 BkmKyX8w 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > > + 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