On Tue, Aug 7, 2018 at 11:18 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > In the quest to remove all stack VLA usage from the kernel[1], this uses > the new upper bound for the stack buffer. Also adds a sanity check. > > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> After rebasing to linux-next, I now get a warning about this file: drivers/crypto/qat/qat_common/qat_algs.c: In function 'qat_alg_do_precomputes': drivers/crypto/qat/qat_common/qat_algs.c:257:1: error: the frame size of 1112 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] I assume it was already possible to get into that state with the VLA, but it seems bad enough that I think we need to do something about it. The large stack variables add up to 1084 bytes, which fully explains how we got here: SHASH_DESC_ON_STACK(shash, ctx->hash_tfm); /* 360 */ struct sha1_state sha1; /* 92 */ struct sha256_state sha256; /* 104 */ struct sha512_state sha512; /* 208 */ char ipad[MAX_ALGAPI_BLOCKSIZE]; /* 160 */ char opad[MAX_ALGAPI_BLOCKSIZE]; /* 160 */ The question is what we can do about it. One simple step I've tried is to move the sha1/sha256/sha512 into a union, which saves around 200 bytes and should bring us (slightly) below the warning limit, but I suspect we can do better than that. Any ideas? Arnd
