On 18 July 2018 at 05:59, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Sun, Jul 15, 2018 at 6:28 AM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: >> >> After my ahash to shash conversions, only ccm is left as an ahash >> user, since it actually uses sg. But with the hard-coded value reduced >> to 376, this doesn't trip the frame warnings any more. :) >> >> I'll send an updated series soon. > > Maybe we should get rid of that one as well then and remove > AHASH_REQUEST_ON_STACK()? > > I see that Ard (now on Cc) added this usage only recently. Looking > at the code some more, I also find that the descsize is probably > much smaller than 376 for all possible cases of "cbcmac(*)", > either alg->cra_blocksize plus a few bytes or sizeof(mac_desc_ctx) > (i.e. 20) for arch/arm64/crypto/aes-glue.c. > > Walking the sglist here means open-coding a shash_ahash_update() > implementation in crypto_ccm_auth(), that that doesn't seem to > add much complexity over what it already has to do to chain > the sglist today. > It would be better to add a variably sized ahash request member to struct crypto_ccm_req_priv_ctx, the only problem is that the last member of that struct (skreq) is variably sized already, so it would involve having a struct ahash_request pointer pointing into the same struct, after the skreq member.
