From mboxrd@z Thu Jan 1 00:00:00 1970 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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 7297BC433DF for ; Sat, 8 Aug 2020 23:47:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 473BE20672 for ; Sat, 8 Aug 2020 23:47:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596930466; bh=iVo0GPoeKyLafUTHicn9yxl086QZHMa+h8QT9zS3jU8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=fwLb4P1Dkf6mfYMjHqwnV8LmFFzgKJPidTkJqJb+olem6AFCbDish1r5BbKfA54rb AzUQGmBkGRMF2ZY2fRkb7i6msKZySBjcwGv1PpPV66btInxOL8GK0klw4K76/uwUBR QK+FAM2OX+HM43pW1Cj0Ra3XxKYd2hRO8r+VS+gk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727969AbgHHXho (ORCPT ); Sat, 8 Aug 2020 19:37:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:50828 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728047AbgHHXhk (ORCPT ); Sat, 8 Aug 2020 19:37:40 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (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 71DC720716; Sat, 8 Aug 2020 23:37:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596929860; bh=iVo0GPoeKyLafUTHicn9yxl086QZHMa+h8QT9zS3jU8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Rdb+M9pc1YQqHvWz/lhCBsyCsrdbepzpD6fZWRFDOXv7oZG6SMWBCEWoyX5PIDpuJ HPYTQAcpQGXvWIVblSbvfvVayNDFMrdeasV/aVbjLIYAmttBhcZl18XWf4p4NPi6VM mKYfdp9D4+xTGEemLaMkRkB025zgWKHkVu3bdQlY= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Herbert Xu , "Martin K . Petersen" , Eric Biggers , Sasha Levin Subject: [PATCH AUTOSEL 5.7 12/58] crc-t10dif: Fix potential crypto notify dead-lock Date: Sat, 8 Aug 2020 19:36:38 -0400 Message-Id: <20200808233724.3618168-12-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200808233724.3618168-1-sashal@kernel.org> References: <20200808233724.3618168-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Herbert Xu [ Upstream commit 3906f640224dbe7714b52b66d7d68c0812808e19 ] The crypto notify call occurs with a read mutex held so you must not do any substantial work directly. In particular, you cannot call crypto_alloc_* as they may trigger further notifications which may dead-lock in the presence of another writer. This patch fixes this by postponing the work into a work queue and taking the same lock in the module init function. While we're at it this patch also ensures that all RCU accesses are marked appropriately (tested with sparse). Finally this also reveals a race condition in module param show function as it may be called prior to the module init function. It's fixed by testing whether crct10dif_tfm is NULL (this is true iff the init function has not completed assuming fallback is false). Fixes: 11dcb1037f40 ("crc-t10dif: Allow current transform to be...") Fixes: b76377543b73 ("crc-t10dif: Pick better transform if one...") Signed-off-by: Herbert Xu Reviewed-by: Martin K. Petersen Reviewed-by: Eric Biggers Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin --- lib/crc-t10dif.c | 54 +++++++++++++++++++++++++++++++++++++----------- 1 file changed, 42 insertions(+), 12 deletions(-) diff --git a/lib/crc-t10dif.c b/lib/crc-t10dif.c index 8cc01a6034165..c9acf1c12cfcb 100644 --- a/lib/crc-t10dif.c +++ b/lib/crc-t10dif.c @@ -19,39 +19,46 @@ static struct crypto_shash __rcu *crct10dif_tfm; static struct static_key crct10dif_fallback __read_mostly; static DEFINE_MUTEX(crc_t10dif_mutex); +static struct work_struct crct10dif_rehash_work; -static int crc_t10dif_rehash(struct notifier_block *self, unsigned long val, void *data) +static int crc_t10dif_notify(struct notifier_block *self, unsigned long val, void *data) { struct crypto_alg *alg = data; - struct crypto_shash *new, *old; if (val != CRYPTO_MSG_ALG_LOADED || static_key_false(&crct10dif_fallback) || strncmp(alg->cra_name, CRC_T10DIF_STRING, strlen(CRC_T10DIF_STRING))) return 0; + schedule_work(&crct10dif_rehash_work); + return 0; +} + +static void crc_t10dif_rehash(struct work_struct *work) +{ + struct crypto_shash *new, *old; + 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 0; + return; } new = crypto_alloc_shash("crct10dif", 0, 0); if (IS_ERR(new)) { mutex_unlock(&crc_t10dif_mutex); - return 0; + return; } rcu_assign_pointer(crct10dif_tfm, new); mutex_unlock(&crc_t10dif_mutex); synchronize_rcu(); crypto_free_shash(old); - return 0; } static struct notifier_block crc_t10dif_nb = { - .notifier_call = crc_t10dif_rehash, + .notifier_call = crc_t10dif_notify, }; __u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len) @@ -86,19 +93,26 @@ 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); - crct10dif_tfm = crypto_alloc_shash("crct10dif", 0, 0); - if (IS_ERR(crct10dif_tfm)) { + mutex_lock(&crc_t10dif_mutex); + tfm = crypto_alloc_shash("crct10dif", 0, 0); + if (IS_ERR(tfm)) { static_key_slow_inc(&crct10dif_fallback); - crct10dif_tfm = NULL; + tfm = NULL; } + RCU_INIT_POINTER(crct10dif_tfm, tfm); + mutex_unlock(&crc_t10dif_mutex); return 0; } static void __exit crc_t10dif_mod_fini(void) { crypto_unregister_notifier(&crc_t10dif_nb); - crypto_free_shash(crct10dif_tfm); + cancel_work_sync(&crct10dif_rehash_work); + crypto_free_shash(rcu_dereference_protected(crct10dif_tfm, 1)); } module_init(crc_t10dif_mod_init); @@ -106,11 +120,27 @@ module_exit(crc_t10dif_mod_fini); static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp) { + struct crypto_shash *tfm; + const char *name; + int len; + if (static_key_false(&crct10dif_fallback)) return sprintf(buffer, "fallback\n"); - return sprintf(buffer, "%s\n", - crypto_tfm_alg_driver_name(crypto_shash_tfm(crct10dif_tfm))); + 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; } module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0644); -- 2.25.1