Date: Wed, 2 Aug 2017 21:35:04 -0700 From: Kees Cook <keescook@...omium.org> To: Arnd Bergmann <arnd@...db.de> Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>, 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 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? -Kees -- Kees Cook Pixel Security
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