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From: Kees Cook <keescook@chromium.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Giovanni Cabiddu <giovanni.cabiddu@intel.com>,
	Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
	Mike Snitzer <snitzer@redhat.com>,
	Eric Biggers <ebiggers@google.com>,
	qat-linux@intel.com, linux-kernel@vger.kernel.org,
	dm-devel@redhat.com, linux-crypto@vger.kernel.org,
	Lars Persson <larper@axis.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Alasdair Kergon <agk@redhat.com>, Rabin Vincent <rabinv@axis.com>
Subject: [PATCH v5 07/11] crypto alg: Introduce generic max blocksize and alignmask
Date: Mon, 16 Jul 2018 21:21:46 -0700	[thread overview]
Message-ID: <20180717042150.37761-8-keescook@chromium.org> (raw)
In-Reply-To: <20180717042150.37761-1-keescook@chromium.org>

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>
---
 crypto/algapi.c         | 7 ++++++-
 include/crypto/algapi.h | 4 +++-
 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
 
-- 
2.17.1

WARNING: multiple messages have this Message-ID (diff)
From: Kees Cook <keescook@chromium.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
	Eric Biggers <ebiggers@google.com>,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
	Alasdair Kergon <agk@redhat.com>,
	Giovanni Cabiddu <giovanni.cabiddu@intel.com>,
	Lars Persson <larper@axis.com>, Mike Snitzer <snitzer@redhat.com>,
	Rabin Vincent <rabinv@axis.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	linux-crypto@vger.kernel.org, qat-linux@intel.com,
	dm-devel@redhat.com, linux-kernel@vger.kernel.org
Subject: [PATCH v5 07/11] crypto alg: Introduce generic max blocksize and alignmask
Date: Mon, 16 Jul 2018 21:21:46 -0700	[thread overview]
Message-ID: <20180717042150.37761-8-keescook@chromium.org> (raw)
In-Reply-To: <20180717042150.37761-1-keescook@chromium.org>

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>
---
 crypto/algapi.c         | 7 ++++++-
 include/crypto/algapi.h | 4 +++-
 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
 
-- 
2.17.1


  parent reply	other threads:[~2018-07-17  4:21 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-17  4:21 [PATCH v5 00/11] crypto: Remove VLA usage Kees Cook
2018-07-17  4:21 ` Kees Cook
2018-07-17  4:21 ` [PATCH v5 01/11] crypto: xcbc: " Kees Cook
2018-07-17  6:35   ` Herbert Xu
2018-07-17  4:21 ` [PATCH v5 02/11] crypto: cbc: " Kees Cook
2018-07-17  4:21 ` [PATCH v5 03/11] crypto: shash: " Kees Cook
2018-07-17  4:21 ` [PATCH v5 04/11] dm integrity: " Kees Cook
2018-07-17  4:21   ` Kees Cook
2018-07-17  4:21 ` [PATCH v5 05/11] crypto: ahash: " Kees Cook
2018-07-17  4:21   ` Kees Cook
2018-07-17 16:39   ` [dm-devel] " Eric Biggers
2018-07-17 20:07     ` Kees Cook
2018-07-17 23:12       ` Eric Biggers
2018-07-19  3:14         ` Kees Cook
2018-07-17  4:21 ` [PATCH v5 06/11] dm verity fec: " Kees Cook
2018-07-17  4:21 ` Kees Cook [this message]
2018-07-17  4:21   ` [PATCH v5 07/11] crypto alg: Introduce generic max blocksize and alignmask Kees Cook
2018-07-17  4:21 ` [PATCH v5 08/11] crypto: qat: Remove VLA usage Kees Cook
2018-07-17  4:21 ` [PATCH v5 09/11] crypto: shash: Remove VLA usage in unaligned hashing Kees Cook
2018-07-17  4:21 ` [PATCH v5 10/11] crypto: ahash: Remove VLA usage for AHASH_REQUEST_ON_STACK Kees Cook
2018-07-17 16:43   ` [dm-devel] " Eric Biggers
2018-07-17 20:11     ` Kees Cook
2018-07-17  4:21 ` [PATCH v5 11/11] crypto: skcipher: Remove VLA usage for SKCIPHER_REQUEST_ON_STACK Kees Cook

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