Date: Thu, 3 Aug 2017 19:27:25 +0100 From: Ard Biesheuvel <ard.biesheuvel@...aro.org> To: Kees Cook <keescook@...omium.org> Cc: Arnd Bergmann <arnd@...db.de>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [RFC/RFT PATCH] gcc-plugins: force initialize auto variables whose addresses are taken On 3 August 2017 at 05:35, Kees Cook <keescook@...omium.org> wrote: > On Thu, Jul 6, 2017 at 4:16 PM, Kees Cook <keescook@...omium.org> wrote: >> On Thu, Jul 6, 2017 at 2:44 PM, Kees Cook <keescook@...omium.org> wrote: >>> On Thu, Jul 6, 2017 at 4:09 AM, Arnd Bergmann <arnd@...db.de> wrote: >>>> On Thu, Jul 6, 2017 at 12:13 PM, Ard Biesheuvel >>>> <ard.biesheuvel@...aro.org> wrote: >>>>> To prevent leaking stack contents in cases where it is not possible >>>>> for the compiler to figure out whether an automatic variable has been >>>>> initialized or not, add a plugin that forcibly initializes all automatic >>>>> variables of struct/union types if their address is taken at any point. >>>>> >>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org> >>> >>> Ard, I'd be curious what you see for "size" difference between builds >>> and if it's visible with hackbench or other things? >> >> Hm, not all that bad on the size front: >> >> text data bss dec >> hex filename >> 10950705 5592525 13955072 30498302 1d15dfe vmlinux >> 11048035 5592365 13955072 30595472 1d2d990 >> vmlinux.initautobyref >> >> And yes, as expected, wow there are a lot of notices in verbose mode. ;) >> >> My pet favorite, from the NAKed patch I sent forever ago, is covered >> (as expected): >> >> net/socket.c: In function ‘SYSC_getsockname’: >> net/socket.c:1605:26: note: auto variable will be forcibly initialized >> struct sockaddr_storage address; >> ^~~~~~~ > > While this was an RFC, it seems to work well and, as Daniel mentioned, > provides another benchmark for future optimizations of this kind of > protection. Besides the COMPILE_TEST change already discussed, any > other changes or objections before I carry this in -next? > Sounds reasonable to me.
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