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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 1E0B5C433E1 for ; Mon, 17 Aug 2020 19:47:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DEF8520716 for ; Mon, 17 Aug 2020 19:47:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597693634; bh=iVo0GPoeKyLafUTHicn9yxl086QZHMa+h8QT9zS3jU8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=crFTEu+ROJghkSsJ+x3tHozOaXYYqagZgbOHYb/AAUXYyY4XadPbfy3wLxsY6GfPC xMeZAMKfNNGuolYTi3guTLLtiQO3BBWrN0uKWGaks7BIbbyxMA05fbLSbWYMqVmJRU PcW5ygzEaLaMRgu6dPKNxZzVUQ9jKXdshW/nA8es= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732662AbgHQTrM (ORCPT ); Mon, 17 Aug 2020 15:47:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:42684 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729209AbgHQPUu (ORCPT ); Mon, 17 Aug 2020 11:20:50 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B7E23207DE; Mon, 17 Aug 2020 15:20:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597677649; bh=iVo0GPoeKyLafUTHicn9yxl086QZHMa+h8QT9zS3jU8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QPo0jNw3k7/IEj7D9VAbPu2bV/6HqJfGq1vTMNzIx6nI/DBTMKl1O48OraEYS5glM oVTu67Q5QaV88/gXKnV29P8d8DIIV+Qo7PEKjCYydz6OeOZE6AEbZ2kk0D6UQjyOD7 t4qn6ir/BKqz3WRn9Hgy2ROP4gGSyFuNUguIxt98= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Herbert Xu , "Martin K. Petersen" , Eric Biggers , Sasha Levin Subject: [PATCH 5.8 018/464] crc-t10dif: Fix potential crypto notify dead-lock Date: Mon, 17 Aug 2020 17:09:31 +0200 Message-Id: <20200817143834.630795761@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200817143833.737102804@linuxfoundation.org> References: <20200817143833.737102804@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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