On Wed, Jun 20, 2018 at 12:04:04PM -0700, Kees Cook wrote: > In the quest to remove all stack VLA usage from the kernel[1], this uses > the maximum blocksize and adds a sanity check. > > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > --- > crypto/xcbc.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/crypto/xcbc.c b/crypto/xcbc.c > index 25c75af50d3f..016481b1f3ba 100644 > --- a/crypto/xcbc.c > +++ b/crypto/xcbc.c > @@ -65,7 +65,10 @@ static int crypto_xcbc_digest_setkey(struct crypto_shash *parent, > int bs = crypto_shash_blocksize(parent); > u8 *consts = PTR_ALIGN(&ctx->ctx[0], alignmask + 1); > int err = 0; > - u8 key1[bs]; > + u8 key1[CRYPTO_ALG_MAX_BLOCKSIZE]; > + > + if (WARN_ON(bs > sizeof(key1))) > + return -EINVAL; Similarly, why not MAX_CIPHER_BLOCKSIZE? Also, xcbc_create() only allows a 16-byte block size, and you made the API enforce the maximum for algorithms anyway. So I think the extra check here isn't very worthwhile. - Eric
