On Tue, Aug 7, 2018 at 2:47 AM, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote: > On Thu, Aug 02, 2018 at 03:51:45PM -0700, Kees Cook wrote: >> In the quest to remove all stack VLA usage from the kernel[1], this >> uses the upper bounds on blocksize. Since this is always a cipher >> blocksize, use the existing cipher max blocksize. >> >> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx >> >> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> >> --- >> include/crypto/cbc.h | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/include/crypto/cbc.h b/include/crypto/cbc.h >> index f5b8bfc22e6d..47db0aac2ab9 100644 >> --- a/include/crypto/cbc.h >> +++ b/include/crypto/cbc.h >> @@ -113,7 +113,9 @@ static inline int crypto_cbc_decrypt_inplace( >> unsigned int bsize = crypto_skcipher_blocksize(tfm); >> unsigned int nbytes = walk->nbytes; >> u8 *src = walk->src.virt.addr; >> - u8 last_iv[bsize]; >> + u8 last_iv[MAX_CIPHER_BLOCKSIZE]; >> + >> + BUG_ON(bsize > sizeof(last_iv)); > > Ugh, please don't add these BUG_ONs. Add them to the places where > the algorithm is created (if they aren't checking that already). It's already being checked (cra_blocksize vs MAX_CIPHER_BLOCKSIZE) so I was just adding the BUG_ON to catch "impossible" behavior. I'll leave it out in the next revision. -Kees -- Kees Cook Pixel Security
