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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id z9-20020a655a49000000b00373459df190sm58337pgs.35.2022.03.02.12.59.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Mar 2022 12:59:29 -0800 (PST) Date: Wed, 2 Mar 2022 12:59:28 -0800 From: Kees Cook To: Linus Torvalds Cc: Rasmus Villemoes , David Laight , James Bottomley , linux-wireless , "alsa-devel@alsa-project.org" , KVM list , "Gustavo A. R. Silva" , "linux-iio@vger.kernel.org" , "nouveau@lists.freedesktop.org" , dri-devel , Cristiano Giuffrida , "Bos, H.J." , "linux1394-devel@lists.sourceforge.net" , "drbd-dev@lists.linbit.com" , linux-arch , CIFS , "linux-aspeed@lists.ozlabs.org" , linux-scsi , linux-rdma , "linux-staging@lists.linux.dev" , amd-gfx list , Jason Gunthorpe , "intel-wired-lan@lists.osuosl.org" , "kgdb-bugreport@lists.sourceforge.net" , "bcm-kernel-feedback-list@broadcom.com" , Dan Carpenter , Linux Media Mailing List , Arnd Bergman , Linux PM , intel-gfx , Brian Johannesmeyer , Nathan Chancellor , dma , Christophe JAILLET , Jakob Koschel , "v9fs-developer@lists.sourceforge.net" , linux-tegra , Thomas Gleixner , Andy Shevchenko , Linux ARM , "linux-sgx@vger.kernel.org" , linux-block , Netdev , "linux-usb@vger.kernel.org" , "samba-technical@lists.samba.org" , Linux Kernel Mailing List , Linux F2FS Dev Mailing List , "tipc-discussion@lists.sourceforge.net" , Linux Crypto Mailing List , linux-fsdevel , "linux-mediatek@lists.infradead.org" , Andrew Morton , linuxppc-dev , Christian =?iso-8859-1?Q?K=F6nig?= , Mike Rapoport Subject: Re: [PATCH 2/6] treewide: remove using list iterator after loop body as a ptr Message-ID: <202203021256.69D7C4BCA6@keescook> References: <7D0C2A5D-500E-4F38-AD0C-A76E132A390E@kernel.org> <73fa82a20910c06784be2352a655acc59e9942ea.camel@HansenPartnership.com> <7dc860874d434d2288f36730d8ea3312@AcuMS.aculab.com> <0ced2b155b984882b39e895f0211037c@AcuMS.aculab.com> <78ccb184-405e-da93-1e02-078f90d2b9bc@rasmusvillemoes.dk> <202203021158.DB5204A0@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Wed, Mar 02, 2022 at 12:18:45PM -0800, Linus Torvalds wrote: > On Wed, Mar 2, 2022 at 12:07 PM Kees Cook wrote: > > > > I've long wanted to change kfree() to explicitly set pointers to NULL on > > free. https://github.com/KSPP/linux/issues/87 > > We've had this discussion with the gcc people in the past, and gcc > actually has some support for it, but it's sadly tied to the actual > function name (ie gcc has some special-casing for "free()") > > See > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94527 > > for some of that discussion. > > Oh, and I see some patch actually got merged since I looked there last > so that you can mark "deallocator" functions, but I think it's only > for the context matching, not for actually killing accesses to the > pointer afterwards. Ah! I missed that getting added in GCC 11. But yes, there it is: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute Hah, now we may need to split __malloc from __alloc_size. ;) I'd still like the NULL assignment behavior, though, since some things can easily avoid static analysis. -- Kees Cook