linux-kernel - [PATCH 08/11] crypto: qat: Remove VLA usage

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Message-Id: <20180620190408.45104-9-keescook@chromium.org>
Date:   Wed, 20 Jun 2018 12:04:05 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Alasdair Kergon <agk@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Eric Biggers <ebiggers@...gle.com>,
        Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
        Lars Persson <larper@...s.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Rabin Vincent <rabinv@...s.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, qat-linux@...el.com,
        dm-devel@...hat.com, linux-kernel@...r.kernel.org
Subject: [PATCH 08/11] crypto: qat: Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this uses
the upper bound for the stack buffer. Also adds a sanity check. This
additionally raises the stack size limit during the build, to avoid
a compiler warning while keeping it reasonably close to expected stack
size. The warning was just exposing the existing max stack size, so there
is nothing new here; now that it is not hidden in a VLA, the compiler
can see how large it might get.

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

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/crypto/qat/qat_common/Makefile   | 2 ++
 drivers/crypto/qat/qat_common/qat_algs.c | 8 ++++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/qat/qat_common/Makefile b/drivers/crypto/qat/qat_common/Makefile
index 47a8e3d8b81a..c2a042023dde 100644
--- a/drivers/crypto/qat/qat_common/Makefile
+++ b/drivers/crypto/qat/qat_common/Makefile
@@ -19,3 +19,5 @@ intel_qat-objs := adf_cfg.o \
 intel_qat-$(CONFIG_DEBUG_FS) += adf_transport_debug.o
 intel_qat-$(CONFIG_PCI_IOV) += adf_sriov.o adf_pf2vf_msg.o \
 			       adf_vf2pf_msg.o adf_vf_isr.o
+
+CFLAGS_qat_algs.o := $(call cc-option,-Wframe-larger-than=2300)
diff --git a/drivers/crypto/qat/qat_common/qat_algs.c b/drivers/crypto/qat/qat_common/qat_algs.c
index 1138e41d6805..257269126601 100644
--- a/drivers/crypto/qat/qat_common/qat_algs.c
+++ b/drivers/crypto/qat/qat_common/qat_algs.c
@@ -153,8 +153,8 @@ static int qat_alg_do_precomputes(struct icp_qat_hw_auth_algo_blk *hash,
 	struct sha512_state sha512;
 	int block_size = crypto_shash_blocksize(ctx->hash_tfm);
 	int digest_size = crypto_shash_digestsize(ctx->hash_tfm);
-	char ipad[block_size];
-	char opad[block_size];
+	char ipad[CRYPTO_ALG_MAX_BLOCKSIZE];
+	char opad[CRYPTO_ALG_MAX_BLOCKSIZE];
 	__be32 *hash_state_out;
 	__be64 *hash512_state_out;
 	int i, offset;
@@ -164,6 +164,10 @@ static int qat_alg_do_precomputes(struct icp_qat_hw_auth_algo_blk *hash,
 	shash->tfm = ctx->hash_tfm;
 	shash->flags = 0x0;
 
+	if (WARN_ON(block_size > sizeof(ipad) ||
+		    sizeof(ipad) != sizeof(opad)))
+		return -EINVAL;
+
 	if (auth_keylen > block_size) {
 		int ret = crypto_shash_digest(shash, auth_key,
 					      auth_keylen, ipad);
-- 
2.17.1