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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 5BF9EC433E0 for ; Fri, 19 Jun 2020 16:28:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3328C21707 for ; Fri, 19 Jun 2020 16:28:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592584104; bh=drSCwkxaKEuyVsBT1eI8rJ1HWOjQjlxhJwPUrGQNOc8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=V8fDmzz/WZHTAFwMsOEo1F64Q9zlZcuup2Y/osXnP9tVjfM7LP8y48+tCSVbnK8xh BFYnUfCqELZwuqg7PIH8Hdv5b+aWu5y3zvGCQN7apwRB3ioEP7iv4yP3M2dJrdPk2c GMctxc2Qr9iVuX97nQGzhqXQbEnJlfYgzOnCixoI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2394945AbgFSQ2V (ORCPT ); Fri, 19 Jun 2020 12:28:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:50278 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389577AbgFSOz0 (ORCPT ); Fri, 19 Jun 2020 10:55:26 -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 7352B2158C; Fri, 19 Jun 2020 14:55:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592578526; bh=drSCwkxaKEuyVsBT1eI8rJ1HWOjQjlxhJwPUrGQNOc8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tSZrP2Mbm9VzINSR2ZmXK0aQKUs7z9IylNRHEo5F8tOJMSahLqC+qwhuO3KHigdmX GI42iS3DixTByCvPuHMPKffUPCrZWfIUagL1bZIeYIyvzTY4iKOoNGhtEuUuDYlNxn PFZMDKMDQ5BRTUw2oOZxrvW6itcjZwNh9dFSVXLU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Linus Torvalds , Waiman Long , Andrew Morton , Eric Biggers , David Howells , Jarkko Sakkinen , James Morris , "Serge E. Hallyn" , Joe Perches , Matthew Wilcox , David Rientjes , Uladzislau Rezki , Sasha Levin Subject: [PATCH 4.19 025/267] mm: add kvfree_sensitive() for freeing sensitive data objects Date: Fri, 19 Jun 2020 16:30:10 +0200 Message-Id: <20200619141650.070396970@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200619141648.840376470@linuxfoundation.org> References: <20200619141648.840376470@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: Waiman Long [ Upstream commit d4eaa2837851db2bfed572898bfc17f9a9f9151e ] For kvmalloc'ed data object that contains sensitive information like cryptographic keys, we need to make sure that the buffer is always cleared before freeing it. Using memset() alone for buffer clearing may not provide certainty as the compiler may compile it away. To be sure, the special memzero_explicit() has to be used. This patch introduces a new kvfree_sensitive() for freeing those sensitive data objects allocated by kvmalloc(). The relevant places where kvfree_sensitive() can be used are modified to use it. Fixes: 4f0882491a14 ("KEYS: Avoid false positive ENOMEM error on key read") Suggested-by: Linus Torvalds Signed-off-by: Waiman Long Signed-off-by: Andrew Morton Reviewed-by: Eric Biggers Acked-by: David Howells Cc: Jarkko Sakkinen Cc: James Morris Cc: "Serge E. Hallyn" Cc: Joe Perches Cc: Matthew Wilcox Cc: David Rientjes Cc: Uladzislau Rezki Link: http://lkml.kernel.org/r/20200407200318.11711-1-longman@redhat.com Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- include/linux/mm.h | 1 + mm/util.c | 18 ++++++++++++++++++ security/keys/internal.h | 11 ----------- security/keys/keyctl.c | 16 +++++----------- 4 files changed, 24 insertions(+), 22 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index b1092046ebef..05bc5f25ab85 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -601,6 +601,7 @@ static inline void *kvcalloc(size_t n, size_t size, gfp_t flags) } extern void kvfree(const void *addr); +extern void kvfree_sensitive(const void *addr, size_t len); /* * Mapcount of compound page as a whole, does not include mapped sub-pages. diff --git a/mm/util.c b/mm/util.c index 6a24a1025d77..621afcea2bfa 100644 --- a/mm/util.c +++ b/mm/util.c @@ -453,6 +453,24 @@ void kvfree(const void *addr) } EXPORT_SYMBOL(kvfree); +/** + * kvfree_sensitive - Free a data object containing sensitive information. + * @addr: address of the data object to be freed. + * @len: length of the data object. + * + * Use the special memzero_explicit() function to clear the content of a + * kvmalloc'ed object containing sensitive data to make sure that the + * compiler won't optimize out the data clearing. + */ +void kvfree_sensitive(const void *addr, size_t len) +{ + if (likely(!ZERO_OR_NULL_PTR(addr))) { + memzero_explicit((void *)addr, len); + kvfree(addr); + } +} +EXPORT_SYMBOL(kvfree_sensitive); + static inline void *__page_rmapping(struct page *page) { unsigned long mapping; diff --git a/security/keys/internal.h b/security/keys/internal.h index eb50212fbbf8..d1b9c5957000 100644 --- a/security/keys/internal.h +++ b/security/keys/internal.h @@ -306,15 +306,4 @@ static inline void key_check(const struct key *key) #define key_check(key) do {} while(0) #endif - -/* - * Helper function to clear and free a kvmalloc'ed memory object. - */ -static inline void __kvzfree(const void *addr, size_t len) -{ - if (addr) { - memset((void *)addr, 0, len); - kvfree(addr); - } -} #endif /* _INTERNAL_H */ diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index c07c2e2b2478..9394d72a77e8 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -133,10 +133,7 @@ SYSCALL_DEFINE5(add_key, const char __user *, _type, key_ref_put(keyring_ref); error3: - if (payload) { - memzero_explicit(payload, plen); - kvfree(payload); - } + kvfree_sensitive(payload, plen); error2: kfree(description); error: @@ -351,7 +348,7 @@ long keyctl_update_key(key_serial_t id, key_ref_put(key_ref); error2: - __kvzfree(payload, plen); + kvfree_sensitive(payload, plen); error: return ret; } @@ -859,7 +856,7 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) */ if (ret > key_data_len) { if (unlikely(key_data)) - __kvzfree(key_data, key_data_len); + kvfree_sensitive(key_data, key_data_len); key_data_len = ret; continue; /* Allocate buffer */ } @@ -868,7 +865,7 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) ret = -EFAULT; break; } - __kvzfree(key_data, key_data_len); + kvfree_sensitive(key_data, key_data_len); key_put_out: key_put(key); @@ -1170,10 +1167,7 @@ long keyctl_instantiate_key_common(key_serial_t id, keyctl_change_reqkey_auth(NULL); error2: - if (payload) { - memzero_explicit(payload, plen); - kvfree(payload); - } + kvfree_sensitive(payload, plen); error: return ret; } -- 2.25.1