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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id iq1-20020a17090afb4100b002135de3013fsm1805607pjb.32.2022.11.02.12.40.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Nov 2022 12:40:32 -0700 (PDT) Date: Wed, 2 Nov 2022 12:40:31 -0700 From: Kees Cook To: Rasmus Villemoes Cc: Vlastimil Babka , Guenter Roeck , Andy Shevchenko , Paolo Abeni , Geert Uytterhoeven , David Gow , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Nathan Chancellor , Nick Desaulniers , Tom Rix , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH 4/6] string: Add __realloc_size hint to kmemdup() Message-ID: <202211021240.4A97FDE0@keescook> References: <20221101222520.never.109-kees@kernel.org> <20221101223321.1326815-4-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1667418034; a=rsa-sha256; cv=none; b=Jfdd2I69mMVxqBDXdJNXZQ0eLNQjYl7RAysYeVM/xAB88519naXtwt+PUpbzMfCpkUu3o5 5d63dBH8e1iqmKK7BVAGnLoXlfk5kyGqLela8Ll2l0zAUMxvE3TCvlhn38wEUX+uslQYgT pNDvvqJAmNzuq65HYabelE8c4qhE8ho= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=kopbiQPK; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf04.hostedemail.com: domain of keescook@chromium.org designates 209.85.214.170 as permitted sender) smtp.mailfrom=keescook@chromium.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1667418034; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=eB2CkIIW+FvN/Lo/L+v4C4FsoNsh4QvCTpwzE0gzBz4=; b=ky1Jv0LTGRSIblOzITQFkq4LMUxdBVCINra3TCbadDM0gPZDTh9UCPSr2eSBz0LTyxHUwd n12VrSoL7su4k0ptgBQZlD6kRmeFP2Gs0WO96umRfOY0wLrTXxWkfggOY4auAS9kOdYyO4 EJUlsuKtSTVRnyjiGBXt2S3EW47YiVg= X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: E9FC340008 X-Rspam-User: Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=kopbiQPK; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf04.hostedemail.com: domain of keescook@chromium.org designates 209.85.214.170 as permitted sender) smtp.mailfrom=keescook@chromium.org X-Stat-Signature: uufo5x953scgybh148iwb9jysss567sp X-HE-Tag: 1667418033-802918 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Nov 02, 2022 at 10:26:40AM +0100, Rasmus Villemoes wrote: > On 01/11/2022 23.33, Kees Cook wrote: > > Add __realloc_size() hint to kmemdup() so the compiler can reason about > > the length of the returned buffer. (These must not use __alloc_size, > > since those include __malloc which says the contents aren't defined[1]). > > > > [1] https://lore.kernel.org/linux-hardening/d199c2af-06af-8a50-a6a1-00eefa0b67b4@prevas.dk/ > > > > > extern char *kstrndup(const char *s, size_t len, gfp_t gfp); > > -extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __alloc_size(2); > > +extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2); > > What tree is this based on? I see that kmemdup() has grown that bogus > __alloc_size in next-20221101, but in next-20221102 this commit seems to > DTRT, namely > > -extern void *kmemdup(const void *src, size_t len, gfp_t gfp); > +extern void *kmemdup(const void *src, size_t len, gfp_t gfp) > __realloc_size(2); > > (i.e. there should never be an intermediate commit where kmemdup has > __alloc_size()). Right -- I fixed in in my -next tree to not use __alloc_size. -- Kees Cook