From patchwork Wed Jun 10 06:39:42 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 197664 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0B48C433E1 for ; Wed, 10 Jun 2020 06:41:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9FB022081A for ; Wed, 10 Jun 2020 06:41:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591771299; bh=1hpfaBML1OOWVYV6GGLZ2RGNotNScSZu4UBYbMv9bvg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=V/FIMscbDT+EgQYdicMou6YkBlCpuwHrbBlGiXfHxgjTT5RgMpT7YB6G7iESegPjl wuJbu0d5C2VM8MYRXrrhPPY2J84ervUetEvAVdqkOelqdwGjis8/awBUDBDS8/EMM+ 9fdn65/GxIFzCPyB7tBc4M1WQU00x8niFQlSN6+k= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726121AbgFJGli (ORCPT ); Wed, 10 Jun 2020 02:41:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:47844 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726153AbgFJGli (ORCPT ); Wed, 10 Jun 2020 02:41:38 -0400 Received: from sol.hsd1.ca.comcast.net (c-107-3-166-239.hsd1.ca.comcast.net [107.3.166.239]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4600D207ED; Wed, 10 Jun 2020 06:41:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591771297; bh=1hpfaBML1OOWVYV6GGLZ2RGNotNScSZu4UBYbMv9bvg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XeXVlfIKHONmbrFvDPP2Yj5tDMSnhNbbkyzAOPd8FiEt1OL+vNH6cntvGzT8jIGKz A00FIuUtlYCqBoGqG13Xew3nPHjrPNkVwufYhg37p/eNzZrpn+S+KriiMB9c7q+ToD rXN9YTkM6fkBZ2vCwk+hQZ3O9Bbj3vtxJqXCXqU8= From: Eric Biggers To: linux-crypto@vger.kernel.org Cc: "Martin K . Petersen" Subject: [PATCH 1/2] crc-t10dif: use fallback in initial state Date: Tue, 9 Jun 2020 23:39:42 -0700 Message-Id: <20200610063943.378796-2-ebiggers@kernel.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200610063943.378796-1-ebiggers@kernel.org> References: <20200610063943.378796-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org From: Eric Biggers Currently the crc-t10dif module starts out with the fallback disabled and crct10dif_tfm == NULL. crc_t10dif_mod_init() tries to allocate crct10dif_tfm, and if it fails it enables the fallback. This is backwards because it means that any call to crc_t10dif() prior to module_init (which could theoretically happen from built-in code) will crash rather than use the fallback as expected. Also, it means that if the initial tfm allocation fails, then the fallback stays permanently enabled even if a crct10dif implementation is loaded later. Change it to use the more logical solution of starting with the fallback enabled, and disabling the fallback when a tfm gets allocated for the first time. This change also ends up simplifying the code. Also take the opportunity to convert the code to use the new static_key API, which is much less confusing than the old and deprecated one. Cc: Martin K. Petersen Signed-off-by: Eric Biggers --- lib/crc-t10dif.c | 37 ++++++++++--------------------------- 1 file changed, 10 insertions(+), 27 deletions(-) diff --git a/lib/crc-t10dif.c b/lib/crc-t10dif.c index c9acf1c12cfcb4..af3613367ef944 100644 --- a/lib/crc-t10dif.c +++ b/lib/crc-t10dif.c @@ -17,7 +17,7 @@ #include static struct crypto_shash __rcu *crct10dif_tfm; -static struct static_key crct10dif_fallback __read_mostly; +static DEFINE_STATIC_KEY_TRUE(crct10dif_fallback); static DEFINE_MUTEX(crc_t10dif_mutex); static struct work_struct crct10dif_rehash_work; @@ -26,7 +26,6 @@ static int crc_t10dif_notify(struct notifier_block *self, unsigned long val, voi struct crypto_alg *alg = data; if (val != CRYPTO_MSG_ALG_LOADED || - static_key_false(&crct10dif_fallback) || strncmp(alg->cra_name, CRC_T10DIF_STRING, strlen(CRC_T10DIF_STRING))) return 0; @@ -41,10 +40,6 @@ static void crc_t10dif_rehash(struct work_struct *work) mutex_lock(&crc_t10dif_mutex); old = rcu_dereference_protected(crct10dif_tfm, lockdep_is_held(&crc_t10dif_mutex)); - if (!old) { - mutex_unlock(&crc_t10dif_mutex); - return; - } new = crypto_alloc_shash("crct10dif", 0, 0); if (IS_ERR(new)) { mutex_unlock(&crc_t10dif_mutex); @@ -53,8 +48,12 @@ static void crc_t10dif_rehash(struct work_struct *work) rcu_assign_pointer(crct10dif_tfm, new); mutex_unlock(&crc_t10dif_mutex); - synchronize_rcu(); - crypto_free_shash(old); + if (old) { + synchronize_rcu(); + crypto_free_shash(old); + } else { + static_branch_disable(&crct10dif_fallback); + } } static struct notifier_block crc_t10dif_nb = { @@ -69,7 +68,7 @@ __u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len) } desc; int err; - if (static_key_false(&crct10dif_fallback)) + if (static_branch_unlikely(&crct10dif_fallback)) return crc_t10dif_generic(crc, buffer, len); rcu_read_lock(); @@ -93,18 +92,9 @@ EXPORT_SYMBOL(crc_t10dif); static int __init crc_t10dif_mod_init(void) { - struct crypto_shash *tfm; - INIT_WORK(&crct10dif_rehash_work, crc_t10dif_rehash); crypto_register_notifier(&crc_t10dif_nb); - mutex_lock(&crc_t10dif_mutex); - tfm = crypto_alloc_shash("crct10dif", 0, 0); - if (IS_ERR(tfm)) { - static_key_slow_inc(&crct10dif_fallback); - tfm = NULL; - } - RCU_INIT_POINTER(crct10dif_tfm, tfm); - mutex_unlock(&crc_t10dif_mutex); + crc_t10dif_rehash(&crct10dif_rehash_work); return 0; } @@ -124,20 +114,13 @@ static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp const char *name; int len; - if (static_key_false(&crct10dif_fallback)) + if (static_branch_unlikely(&crct10dif_fallback)) return sprintf(buffer, "fallback\n"); rcu_read_lock(); tfm = rcu_dereference(crct10dif_tfm); - if (!tfm) { - len = sprintf(buffer, "init\n"); - goto unlock; - } - name = crypto_tfm_alg_driver_name(crypto_shash_tfm(tfm)); len = sprintf(buffer, "%s\n", name); - -unlock: rcu_read_unlock(); return len;