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authorKees Cook <keescook@chromium.org>2018-08-07 14:18:40 -0700
committerHerbert Xu <herbert@gondor.apana.org.au>2018-09-04 11:35:04 +0800
commita9f7f88a12f1494deca1fd9e173c7ae886d14f91 (patch)
tree23873d32268fd658b1b89833b2074c7bdef32528
parentb68a7ec1e9a3efac53ae26a1658a553825a2375c (diff)
crypto: api - Introduce generic max blocksize and alignmask
In the quest to remove all stack VLA usage from the kernel[1], this exposes a new general upper bound on crypto blocksize and alignmask (higher than for the existing cipher limits) for VLA removal, and introduces new checks. At present, the highest cra_alignmask in the kernel is 63. The highest cra_blocksize is 144 (SHA3_224_BLOCK_SIZE, 18 8-byte words). For the new blocksize limit, I went with 160 (20 8-byte words). [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
-rw-r--r--crypto/algapi.c7
-rw-r--r--include/crypto/algapi.h4
2 files changed, 9 insertions, 2 deletions
diff --git a/crypto/algapi.c b/crypto/algapi.c
index c0755cf4f53f..496fc51bf215 100644
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -57,9 +57,14 @@ static int crypto_check_alg(struct crypto_alg *alg)
if (alg->cra_alignmask & (alg->cra_alignmask + 1))
return -EINVAL;
- if (alg->cra_blocksize > PAGE_SIZE / 8)
+ /* General maximums for all algs. */
+ if (alg->cra_alignmask > MAX_ALGAPI_ALIGNMASK)
return -EINVAL;
+ if (alg->cra_blocksize > MAX_ALGAPI_BLOCKSIZE)
+ return -EINVAL;
+
+ /* Lower maximums for specific alg types. */
if (!alg->cra_type && (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) ==
CRYPTO_ALG_TYPE_CIPHER) {
if (alg->cra_alignmask > MAX_CIPHER_ALIGNMASK)
diff --git a/include/crypto/algapi.h b/include/crypto/algapi.h
index bd5e8ccf1687..21371ac8f355 100644
--- a/include/crypto/algapi.h
+++ b/include/crypto/algapi.h
@@ -20,8 +20,10 @@
/*
* Maximum values for blocksize and alignmask, used to allocate
* static buffers that are big enough for any combination of
- * ciphers and architectures.
+ * algs and architectures. Ciphers have a lower maximum size.
*/
+#define MAX_ALGAPI_BLOCKSIZE 160
+#define MAX_ALGAPI_ALIGNMASK 63
#define MAX_CIPHER_BLOCKSIZE 16
#define MAX_CIPHER_ALIGNMASK 15