Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S969674AbdDTHDx (ORCPT ); Thu, 20 Apr 2017 03:03:53 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:45984 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S941998AbdDTGiK (ORCPT ); Thu, 20 Apr 2017 02:38:10 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro , Heiko Carstens , Martin Schwidefsky Subject: [PATCH 3.18 029/124] s390/uaccess: get_user() should zero on failure (again) Date: Thu, 20 Apr 2017 08:35:04 +0200 Message-Id: <20170420063558.166821301@linuxfoundation.org> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170420063557.021306233@linuxfoundation.org> References: <20170420063557.021306233@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1598 Lines: 44 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Heiko Carstens commit d09c5373e8e4eaaa09233552cbf75dc4c4f21203 upstream. Commit fd2d2b191fe7 ("s390: get_user() should zero on failure") intended to fix s390's get_user() implementation which did not zero the target operand if the read from user space faulted. Unfortunately the patch has no effect: the corresponding inline assembly specifies that the operand is only written to ("=") and the previous value is discarded. Therefore the compiler is free to and actually does omit the zero initialization. To fix this simply change the contraint modifier to "+", so the compiler cannot omit the initialization anymore. Fixes: c9ca78415ac1 ("s390/uaccess: provide inline variants of get_user/put_user") Fixes: fd2d2b191fe7 ("s390: get_user() should zero on failure") Cc: Al Viro Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- arch/s390/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/s390/include/asm/uaccess.h +++ b/arch/s390/include/asm/uaccess.h @@ -148,7 +148,7 @@ unsigned long __must_check __copy_to_use " jg 2b\n" \ ".popsection\n" \ EX_TABLE(0b,3b) EX_TABLE(1b,3b) \ - : "=d" (__rc), "=Q" (*(to)) \ + : "=d" (__rc), "+Q" (*(to)) \ : "d" (size), "Q" (*(from)), \ "d" (__reg0), "K" (-EFAULT) \ : "cc"); \