Date: Wed, 8 Nov 2017 17:11:23 -0800 From: Kees Cook <keescook@...omium.org> To: Rasmus Villemoes <linux@...musvillemoes.dk> Cc: kernel-hardening@...ts.openwall.com, LKML <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [RFC 0/6] some compile- and run-time format checking On Wed, Nov 8, 2017 at 2:30 PM, Rasmus Villemoes <linux@...musvillemoes.dk> wrote: > Consider these strictly RFC/POC. > > I tried resurrecting my format_template plugin from two years ago, and > it rebased pretty cleanly. It also compiles with gcc 6.3, and has the > expected effect when one tries to trigger it, so it seems to work ok > (I think there was some build bot issue back then, maybe there still > is). > > The last four patches are something I threw together rather quickly. > They compile and the few test cases pass, but I obviously need to find > some places to actually use fmtcheck() to see if it's worth adding. > > Rasmus Villemoes (6): > plugins: implement format_template attribute > compiler.h: add __format_template Could you split these two off and send separately? This seems like a fine thing to get in now. Probably the second patch should be split up between adding __format_template, and additions of its usage. Do you have any good ways to find and extract all the dynamic format strings we need to mark? > compiler.h: add __attribute__((format_arg)) shorthand > lib/vsprintf.c: add fmtcheck utility > kernel.h: implement fmtmatch() wrapper around fmtcheck() > lib/test_printf.c: add a few fmtcheck() test cases I like this approach a lot. Combined with checking if a format string is in read-only memory, this could really close the door on format string exposures. Thanks! -Kees > > arch/Kconfig | 18 ++ > drivers/hwmon/applesmc.c | 2 +- > drivers/staging/speakup/spk_types.h | 2 +- > include/linux/compiler-gcc.h | 1 + > include/linux/compiler.h | 10 + > include/linux/kernel.h | 13 ++ > include/linux/smpboot.h | 2 +- > include/linux/usb.h | 2 +- > lib/test_printf.c | 41 ++++ > lib/vsprintf.c | 63 +++++ > scripts/Makefile.gcc-plugins | 2 + > scripts/gcc-plugins/format_template_plugin.c | 331 +++++++++++++++++++++++++++ > 12 files changed, 483 insertions(+), 4 deletions(-) > create mode 100644 scripts/gcc-plugins/format_template_plugin.c > > -- > 2.11.0 > -- Kees Cook Pixel Security
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