| Message ID | 20180802225152.19194-3-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | Mike Snitzer |
| Headers | show |
| Series | crypto: Remove VLA usage | expand |
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@mail.gmail.com > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > 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). Thanks,
On Tue, Aug 7, 2018 at 2:47 AM, Herbert Xu <herbert@gondor.apana.org.au> 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@mail.gmail.com >> >> Signed-off-by: Kees Cook <keescook@chromium.org> >> --- >> 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
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)); /* Start of the last block. */ src += nbytes - (nbytes & (bsize - 1)) - bsize;
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@mail.gmail.com Signed-off-by: Kees Cook <keescook@chromium.org> --- include/crypto/cbc.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)