Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932685AbcKIKsm (ORCPT ); Wed, 9 Nov 2016 05:48:42 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:52904 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752325AbcKIKpe (ORCPT ); Wed, 9 Nov 2016 05:45:34 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org Subject: [PATCH 4.4 27/69] Fix potential infoleak in older kernels Date: Wed, 9 Nov 2016 11:44:05 +0100 Message-Id: <20161109102902.269720969@linuxfoundation.org> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161109102901.127641653@linuxfoundation.org> References: <20161109102901.127641653@linuxfoundation.org> User-Agent: quilt/0.64 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: 2098 Lines: 65 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Linus Torvalds Not upstream as it is not needed there. So a patch something like this might be a safe way to fix the potential infoleak in older kernels. THIS IS UNTESTED. It's a very obvious patch, though, so if it compiles it probably works. It just initializes the output variable with 0 in the inline asm description, instead of doing it in the exception handler. It will generate slightly worse code (a few unnecessary ALU operations), but it doesn't have any interactions with the exception handler implementation. Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/uaccess.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -332,7 +332,7 @@ do { \ #define __get_user_asm_u64(x, ptr, retval, errret) \ __get_user_asm(x, ptr, retval, "q", "", "=r", errret) #define __get_user_asm_ex_u64(x, ptr) \ - __get_user_asm_ex(x, ptr, "q", "", "=r") + __get_user_asm_ex(x, ptr, "q", "", "=&r") #endif #define __get_user_size(x, ptr, size, retval, errret) \ @@ -375,13 +375,13 @@ do { \ __chk_user_ptr(ptr); \ switch (size) { \ case 1: \ - __get_user_asm_ex(x, ptr, "b", "b", "=q"); \ + __get_user_asm_ex(x, ptr, "b", "b", "=&q"); \ break; \ case 2: \ - __get_user_asm_ex(x, ptr, "w", "w", "=r"); \ + __get_user_asm_ex(x, ptr, "w", "w", "=&r"); \ break; \ case 4: \ - __get_user_asm_ex(x, ptr, "l", "k", "=r"); \ + __get_user_asm_ex(x, ptr, "l", "k", "=&r"); \ break; \ case 8: \ __get_user_asm_ex_u64(x, ptr); \ @@ -395,7 +395,7 @@ do { \ asm volatile("1: mov"itype" %1,%"rtype"0\n" \ "2:\n" \ _ASM_EXTABLE_EX(1b, 2b) \ - : ltype(x) : "m" (__m(addr))) + : ltype(x) : "m" (__m(addr)), "0" (0)) #define __put_user_nocheck(x, ptr, size) \ ({ \