Messages in this thread | | | From | Kees Cook <> | Date | Wed, 20 Jun 2018 13:36:45 -0700 | Subject | Re: [PATCH 01/11] crypto: shash: Remove VLA usage |
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On Wed, Jun 20, 2018 at 12:30 PM, Christophe Leroy <christophe.leroy@c-s.fr> wrote: > > > On 06/20/2018 07:03 PM, Kees Cook wrote: >> >> In the quest to remove all stack VLA usage from the kernel[1], this >> removes the VLAs in SHASH_DESC_ON_STACK (via crypto_shash_descsize()) >> by using the maximum allowable size (which is now more clearly captured >> in a macro). Similar limits are turned into macros as well. >> >> [1] >> https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com >> >> Signed-off-by: Kees Cook <keescook@chromium.org> > > > Got the following warnings: > > crypto/testmgr.c: In function ‘alg_test_crc32c.part.4’: > crypto/testmgr.c:1896:1: warning: the frame size of 2088 bytes is larger > than 1024 bytes [-Wframe-larger-than=] > crypto/hmac.c: In function ‘hmac_setkey’: > crypto/hmac.c:88:1: warning: the frame size of 2088 bytes is larger than > 1024 bytes [-Wframe-larger-than=]
Ah yes. I didn't do 32-bit builds. So, here's the issue: this uncovers the frame size problems that were hidden by in being a VLA before. It was always possible for the frame to get this big, it's just that the compiler couldn't see it.
For qat, I raised the -Wframe-larger-than flag. It seems we'll need to do this in some other places too.
-Kees
-- Kees Cook Pixel Security
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