From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Gustavo A. R. Silva" Subject: [PATCH] Bluetooth: Remove VLA usage in aes_cmac Date: Tue, 20 Mar 2018 18:34:44 -0500 Message-ID: <20180320233444.GA14446@embeddedor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" To: Marcel Holtmann , Johan Hedberg , "David S. Miller" Return-path: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org In preparation to enabling -Wvla, remove VLA and replace it with dynamic memory allocation instead. The use of stack Variable Length Arrays needs to be avoided, as they can be a vector for stack exhaustion, which can be both a runtime bug or a security flaw. Also, in general, as code evolves it is easy to lose track of how big a VLA can get. Thus, we can end up having runtime failures that are hard to debug. Also, fixed as part of the directive to remove all VLAs from the kernel: https://lkml.org/lkml/2018/3/7/621 Signed-off-by: Gustavo A. R. Silva --- net/bluetooth/smp.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c index a2ddae2..23c694d 100644 --- a/net/bluetooth/smp.c +++ b/net/bluetooth/smp.c @@ -173,7 +173,7 @@ static int aes_cmac(struct crypto_shash *tfm, const u8 k[16], const u8 *m, size_t len, u8 mac[16]) { uint8_t tmp[16], mac_msb[16], msg_msb[CMAC_MSG_MAX]; - SHASH_DESC_ON_STACK(desc, tfm); + struct shash_desc *shash; int err; if (len > CMAC_MSG_MAX) @@ -184,8 +184,13 @@ static int aes_cmac(struct crypto_shash *tfm, const u8 k[16], const u8 *m, return -EINVAL; } - desc->tfm = tfm; - desc->flags = 0; + shash = kzalloc(sizeof(*shash) + crypto_shash_descsize(tfm), + GFP_KERNEL); + if (!shash) + return -ENOMEM; + + shash->tfm = tfm; + shash->flags = 0; /* Swap key and message from LSB to MSB */ swap_buf(k, tmp, 16); @@ -200,8 +205,9 @@ static int aes_cmac(struct crypto_shash *tfm, const u8 k[16], const u8 *m, return err; } - err = crypto_shash_digest(desc, msg_msb, len, mac_msb); - shash_desc_zero(desc); + err = crypto_shash_digest(shash, msg_msb, len, mac_msb); + shash_desc_zero(shash); + kfree(shash); if (err) { BT_ERR("Hash computation error %d", err); return err; -- 2.7.4