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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 67AD6C433DF for ; Thu, 4 Jun 2020 23:48:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BB35820870 for ; Thu, 4 Jun 2020 23:48:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="xgd6mTDv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB35820870 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 63583280026; Thu, 4 Jun 2020 19:48:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5E6D8280005; Thu, 4 Jun 2020 19:48:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 522F8280026; Thu, 4 Jun 2020 19:48:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0215.hostedemail.com [216.40.44.215]) by kanga.kvack.org (Postfix) with ESMTP id 39877280005 for ; Thu, 4 Jun 2020 19:48:24 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 0B9A13751 for ; Thu, 4 Jun 2020 23:48:24 +0000 (UTC) X-FDA: 76893170928.06.unit84_500519d26d9b Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id DC1B610035112 for ; Thu, 4 Jun 2020 23:48:23 +0000 (UTC) X-HE-Tag: unit84_500519d26d9b X-Filterd-Recvd-Size: 6140 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf10.hostedemail.com (Postfix) with ESMTP for ; Thu, 4 Jun 2020 23:48:23 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 5712E2086A; Thu, 4 Jun 2020 23:48:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591314502; bh=NWDNtcg5pdEqqpxUCN+iiEZ3rnVWyQ6BkHcGwU6Bv8A=; h=Date:From:To:Subject:In-Reply-To:From; b=xgd6mTDvz/WsoD+aDrMp/Zg4lz9LdBvUtE7h5YBQB48s1Hn7/8SKCzeLTnXmIn5WC Me/rqU2RpQG09VxGdTkxyeiQrHGCykhd7yF6omigB1sCzVgBgzr9/m2SC0ur3ONmgA Ano4PdVtE33mXCQEH9TU9ZVJQMdK7MEh5NKBZFiE= Date: Thu, 04 Jun 2020 16:48:21 -0700 From: Andrew Morton To: akpm@linux-foundation.org, dhowells@redhat.com, ebiggers@google.com, jarkko.sakkinen@linux.intel.com, jmorris@namei.org, joe@perches.com, linux-mm@kvack.org, longman@redhat.com, mm-commits@vger.kernel.org, rientjes@google.com, serge@hallyn.com, torvalds@linux-foundation.org, urezki@gmail.com, willy@infradead.org Subject: [patch 041/127] mm: add kvfree_sensitive() for freeing sensitive data objects Message-ID: <20200604234821.eW1nawh1U%akpm@linux-foundation.org> In-Reply-To: <20200604164523.e15f3177f4b69dcb4f2534a1@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Rspamd-Queue-Id: DC1B610035112 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Waiman Long Subject: mm: add kvfree_sensitive() for freeing sensitive data objects 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. Link: http://lkml.kernel.org/r/20200407200318.11711-1-longman@redhat.com Fixes: 4f0882491a14 ("KEYS: Avoid false positive ENOMEM error on key read") Signed-off-by: Waiman Long Suggested-by: Linus Torvalds 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 Signed-off-by: Andrew Morton --- 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(-) --- a/include/linux/mm.h~mm-add-kvfree_sensitive-for-freeing-sensitive-data-objects +++ a/include/linux/mm.h @@ -776,6 +776,7 @@ static inline void *kvcalloc(size_t n, s } 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. --- a/mm/util.c~mm-add-kvfree_sensitive-for-freeing-sensitive-data-objects +++ a/mm/util.c @@ -604,6 +604,24 @@ 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; --- a/security/keys/internal.h~mm-add-kvfree_sensitive-for-freeing-sensitive-data-objects +++ a/security/keys/internal.h @@ -350,15 +350,4 @@ static inline void key_check(const struc #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 */ --- a/security/keys/keyctl.c~mm-add-kvfree_sensitive-for-freeing-sensitive-data-objects +++ a/security/keys/keyctl.c @@ -142,10 +142,7 @@ SYSCALL_DEFINE5(add_key, const char __us key_ref_put(keyring_ref); error3: - if (payload) { - memzero_explicit(payload, plen); - kvfree(payload); - } + kvfree_sensitive(payload, plen); error2: kfree(description); error: @@ -360,7 +357,7 @@ long keyctl_update_key(key_serial_t id, key_ref_put(key_ref); error2: - __kvzfree(payload, plen); + kvfree_sensitive(payload, plen); error: return ret; } @@ -914,7 +911,7 @@ can_read_key: */ 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 */ } @@ -923,7 +920,7 @@ can_read_key: ret = -EFAULT; break; } - __kvzfree(key_data, key_data_len); + kvfree_sensitive(key_data, key_data_len); key_put_out: key_put(key); @@ -1225,10 +1222,7 @@ long keyctl_instantiate_key_common(key_s keyctl_change_reqkey_auth(NULL); error2: - if (payload) { - memzero_explicit(payload, plen); - kvfree(payload); - } + kvfree_sensitive(payload, plen); error: return ret; } _