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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>, Rabin Vincent <rabinv@axis.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Pavel Machek <pavel@ucw.cz>, Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Philipp Reisner <philipp.reisner@linbit.com>,
	Lars Ellenberg <lars.ellenberg@linbit.com>,
	Jens Axboe <axboe@kernel.dk>,
	Giovanni Cabiddu <giovanni.cabiddu@intel.com>,
	Mike Snitzer <snitzer@redhat.com>,
	Paul Mackerras <paulus@samba.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	David Howells <dhowells@redhat.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	Tudor-Dan Ambarus <tudor.ambarus@microchip.com>,
	Jia-Ju Bai <baijiaju1990@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Will Deacon <will.deacon@arm.com>,
	dm-devel@redhat.com, linux-pm@vger.kernel.org,
	linux-crypto@vger.kernel.org, drbd-dev@lists.linbit.com,
	linux-block@vger.kernel.org, qat-linux@intel.com,
	linux-ppp@vger.kernel.org, netdev@vger.kernel.org,
	devel@driverdev.osuosl.org, linux-afs@lists.infradead.org,
	linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v6 07/18] crypto: shash: Remove VLA usage in unaligned hashing
Date: Tue, 24 Jul 2018 16:49:25 +0000	[thread overview]
Message-ID: <20180724164936.37477-8-keescook@chromium.org> (raw)
In-Reply-To: <20180724164936.37477-1-keescook@chromium.org>

In the quest to remove all stack VLA usage from the kernel[1], this uses
the newly defined max alignment to perform unaligned hashing to avoid
VLAs, and drops the helper function while adding sanity checks on the
resulting buffer sizes. Additionally, the __aligned_largest macro is
removed since this helper was the only user.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 crypto/shash.c               | 27 ++++++++++++++++-----------
 include/linux/compiler-gcc.h |  1 -
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/crypto/shash.c b/crypto/shash.c
index 86d76b5c626c..d21f04d70dce 100644
--- a/crypto/shash.c
+++ b/crypto/shash.c
@@ -73,13 +73,6 @@ int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key,
 }
 EXPORT_SYMBOL_GPL(crypto_shash_setkey);
 
-static inline unsigned int shash_align_buffer_size(unsigned len,
-						   unsigned long mask)
-{
-	typedef u8 __aligned_largest u8_aligned;
-	return len + (mask & ~(__alignof__(u8_aligned) - 1));
-}
-
 static int shash_update_unaligned(struct shash_desc *desc, const u8 *data,
 				  unsigned int len)
 {
@@ -88,11 +81,17 @@ static int shash_update_unaligned(struct shash_desc *desc, const u8 *data,
 	unsigned long alignmask = crypto_shash_alignmask(tfm);
 	unsigned int unaligned_len = alignmask + 1 -
 				     ((unsigned long)data & alignmask);
-	u8 ubuf[shash_align_buffer_size(unaligned_len, alignmask)]
-		__aligned_largest;
+	/*
+	 * We cannot count on __aligned() working for large values:
+	 * https://patchwork.kernel.org/patch/9507697/
+	 */
+	u8 ubuf[MAX_ALGAPI_ALIGNMASK * 2];
 	u8 *buf = PTR_ALIGN(&ubuf[0], alignmask + 1);
 	int err;
 
+	if (WARN_ON(buf + unaligned_len > ubuf + sizeof(ubuf)))
+		return -EINVAL;
+
 	if (unaligned_len > len)
 		unaligned_len = len;
 
@@ -124,11 +123,17 @@ static int shash_final_unaligned(struct shash_desc *desc, u8 *out)
 	unsigned long alignmask = crypto_shash_alignmask(tfm);
 	struct shash_alg *shash = crypto_shash_alg(tfm);
 	unsigned int ds = crypto_shash_digestsize(tfm);
-	u8 ubuf[shash_align_buffer_size(ds, alignmask)]
-		__aligned_largest;
+	/*
+	 * We cannot count on __aligned() working for large values:
+	 * https://patchwork.kernel.org/patch/9507697/
+	 */
+	u8 ubuf[MAX_ALGAPI_ALIGNMASK + HASH_MAX_DIGESTSIZE];
 	u8 *buf = PTR_ALIGN(&ubuf[0], alignmask + 1);
 	int err;
 
+	if (WARN_ON(buf + ds > ubuf + sizeof(ubuf)))
+		return -EINVAL;
+
 	err = shash->final(desc, buf);
 	if (err)
 		goto out;
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index f1a7492a5cc8..1f1cdef36a82 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -125,7 +125,6 @@
  */
 #define __pure			__attribute__((pure))
 #define __aligned(x)		__attribute__((aligned(x)))
-#define __aligned_largest	__attribute__((aligned))
 #define __printf(a, b)		__attribute__((format(printf, a, b)))
 #define __scanf(a, b)		__attribute__((format(scanf, a, b)))
 #define __attribute_const__	__attribute__((__const__))
-- 
2.17.1


  parent reply	other threads:[~2018-07-24 16:49 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-24 16:49 [PATCH v6 00/18] crypto: Remove VLA usage Kees Cook
2018-07-24 16:49 ` [PATCH v6 01/18] crypto: xcbc: " Kees Cook
2018-07-24 16:49 ` [PATCH v6 02/18] crypto: cbc: " Kees Cook
2018-07-24 16:49 ` [PATCH v6 03/18] crypto: hash: " Kees Cook
2018-07-24 16:49 ` [PATCH v6 04/18] dm: Remove VLA usage from hashes Kees Cook
2018-07-24 16:49 ` [PATCH v6 05/18] crypto alg: Introduce generic max blocksize and alignmask Kees Cook
2018-07-24 16:49 ` [PATCH v6 06/18] crypto: qat: Remove VLA usage Kees Cook
2018-07-24 16:49 ` Kees Cook [this message]
2018-07-24 16:49 ` [PATCH v6 08/18] crypto: skcipher: Remove VLA usage for SKCIPHER_REQUEST_ON_STACK Kees Cook
2018-07-24 16:49 ` [PATCH v6 09/18] ppp: mppe: Remove VLA usage Kees Cook
2018-07-24 16:49 ` [PATCH v6 10/18] x86/power/64: " Kees Cook
2018-07-25 11:32   ` Rafael J. Wysocki
2018-07-25 18:01     ` Kees Cook
2018-08-06 10:28       ` Rafael J. Wysocki
2018-07-24 16:49 ` [PATCH v6 11/18] dm crypt: Convert essiv from ahash to shash Kees Cook
2018-07-24 16:49 ` [PATCH v6 12/18] drbd: Convert " Kees Cook
2018-07-24 16:49 ` [PATCH v6 13/18] wireless/lib80211: " Kees Cook
2018-07-25  7:24   ` Johannes Berg
2018-07-24 16:49 ` [PATCH v6 14/18] staging: rtl8192u: ieee80211: " Kees Cook
2018-07-24 16:49 ` [PATCH v6 15/18] staging: rtl8192e: " Kees Cook
2018-07-24 16:49 ` [PATCH v6 16/18] rxrpc: Reuse SKCIPHER_REQUEST_ON_STACK buffer Kees Cook
2018-07-24 16:49 ` [PATCH v6 17/18] crypto: ccm: Remove VLA usage Kees Cook
2018-07-24 16:57   ` Ard Biesheuvel
2018-07-24 17:51     ` Kees Cook
2018-07-24 16:49 ` [PATCH v6 18/18] crypto: Remove AHASH_REQUEST_ON_STACK Kees Cook
2018-07-24 17:31   ` Joe Perches
2018-07-24 17:53     ` Kees Cook

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