On Wed, Jun 20, 2018 at 1:39 PM, Christophe LEROY <christophe.leroy@xxxxxx> wrote: > > > Le 20/06/2018 à 22:36, Kees Cook a écrit : >> >> On Wed, Jun 20, 2018 at 12:30 PM, Christophe Leroy >> <christophe.leroy@xxxxxx> 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@xxxxxxxxxxxxxx >>>> >>>> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> >>> >>> >>> >>> 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. > > > Maybe the issue is because I have selected 16k pages ? That would do it! And that's exactly the problem Arnd mentioned. For v2, I will switch all the PAGE_SIZE-related limits to an explicit 512. (And I'll do some 32-bit builds too to see if any other cases pop up that I need to mask out.) -Kees -- Kees Cook Pixel Security
