| Message ID | 20180717042150.37761-2-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | Mike Snitzer |
| Headers | show |
On Mon, Jul 16, 2018 at 09:21:40PM -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. For xcbc, the blocksize > must always be 16, so use that, since it's already being enforced during > instantiation. > > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > crypto/xcbc.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/crypto/xcbc.c b/crypto/xcbc.c > index 25c75af50d3f..7aa03beed795 100644 > --- a/crypto/xcbc.c > +++ b/crypto/xcbc.c > @@ -57,6 +57,8 @@ struct xcbc_desc_ctx { > u8 ctx[]; > }; > > +#define XCBC_BLOCKSIZE 16 > + > static int crypto_xcbc_digest_setkey(struct crypto_shash *parent, > const u8 *inkey, unsigned int keylen) > { > @@ -65,7 +67,10 @@ 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[XCBC_BLOCKSIZE]; > + > + if (WARN_ON(bs > sizeof(key1))) > + return -EINVAL; Please remove this. You already checked it in xcbc_create. In fact, you should just make bs XCBC_BLOCKSIZE unconditinoally in this function. Cheers,
diff --git a/crypto/xcbc.c b/crypto/xcbc.c index 25c75af50d3f..7aa03beed795 100644 --- a/crypto/xcbc.c +++ b/crypto/xcbc.c @@ -57,6 +57,8 @@ struct xcbc_desc_ctx { u8 ctx[]; }; +#define XCBC_BLOCKSIZE 16 + static int crypto_xcbc_digest_setkey(struct crypto_shash *parent, const u8 *inkey, unsigned int keylen) { @@ -65,7 +67,10 @@ 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[XCBC_BLOCKSIZE]; + + if (WARN_ON(bs > sizeof(key1))) + return -EINVAL; if ((err = crypto_cipher_setkey(ctx->child, inkey, keylen))) return err; @@ -212,7 +217,7 @@ static int xcbc_create(struct crypto_template *tmpl, struct rtattr **tb) return PTR_ERR(alg); switch(alg->cra_blocksize) { - case 16: + case XCBC_BLOCKSIZE: break; default: goto out_put_alg;
In the quest to remove all stack VLA usage from the kernel[1], this uses the maximum blocksize and adds a sanity check. For xcbc, the blocksize must always be 16, so use that, since it's already being enforced during instantiation. [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook <keescook@chromium.org> --- crypto/xcbc.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)