Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932597AbbFCL4q (ORCPT ); Wed, 3 Jun 2015 07:56:46 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:56234 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754307AbbFCLnt (ORCPT ); Wed, 3 Jun 2015 07:43:49 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Kara , Linus Torvalds Subject: [PATCH 3.10 13/46] lib: Fix strnlen_user() to not touch memory after specified maximum Date: Wed, 3 Jun 2015 20:42:51 +0900 Message-Id: <20150603063400.212725406@linuxfoundation.org> X-Mailer: git-send-email 2.4.2 In-Reply-To: <20150603063357.922683803@linuxfoundation.org> References: <20150603063357.922683803@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1465 Lines: 43 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jan Kara commit f18c34e483ff6b1d9866472221e4015b3a4698e4 upstream. If the specified maximum length of the string is a multiple of unsigned long, we would load one long behind the specified maximum. If that happens to be in a next page, we can hit a page fault although we were not expected to. Fix the off-by-one bug in the test whether we are at the end of the specified range. Signed-off-by: Jan Kara Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- lib/strnlen_user.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/lib/strnlen_user.c +++ b/lib/strnlen_user.c @@ -57,7 +57,8 @@ static inline long do_strnlen_user(const return res + find_zero(data) + 1 - align; } res += sizeof(unsigned long); - if (unlikely(max < sizeof(unsigned long))) + /* We already handled 'unsigned long' bytes. Did we do it all ? */ + if (unlikely(max <= sizeof(unsigned long))) break; max -= sizeof(unsigned long); if (unlikely(__get_user(c,(unsigned long __user *)(src+res)))) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/