Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934227AbbDXTxh (ORCPT ); Fri, 24 Apr 2015 15:53:37 -0400 Received: from cantor2.suse.de ([195.135.220.15]:46723 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933628AbbDXTxg (ORCPT ); Fri, 24 Apr 2015 15:53:36 -0400 Date: Fri, 24 Apr 2015 21:53:31 +0200 (CEST) From: Jiri Kosina To: Josh Poimboeuf , Seth Jennings , Vojtech Pavlik cc: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] livepatch: x86: make kASLR logic more accurate Message-ID: User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2802 Lines: 80 We give up old_addr hint from the coming patch module in cases when kernel load base has been randomized (as in such case, the coming module has no idea about the exact randomization offset). We are currently too pessimistic, and give up immediately as soon as CONFIG_RANDOMIZE_BASE is set; this doesn't however directly imply that the load base has actually been randomized. There are config options that disable kASLR (such as hibernation), user could have disabled kaslr on kernel command-line, etc. The loader propagates the information whether kernel has been randomized through bootparams. This allows us to have the condition more accurate. On top of that, it seems unnecessary to give up old_addr hints even if randomization is active. The relocation offset can be computed as difference between _text start and __START_KERNEL, and therefore old_addr can be adjusted accordingly. Signed-off-by: Jiri Kosina --- arch/x86/include/asm/livepatch.h | 4 ++++ arch/x86/kernel/livepatch.c | 5 +++++ kernel/livepatch/core.c | 5 +++-- 3 files changed, 12 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/livepatch.h b/arch/x86/include/asm/livepatch.h index 2d29197..3c339c0 100644 --- a/arch/x86/include/asm/livepatch.h +++ b/arch/x86/include/asm/livepatch.h @@ -23,8 +23,12 @@ #include #include +#include #ifdef CONFIG_LIVEPATCH + +extern unsigned long kgr_vmlinux_relocation_offset(void); + static inline int klp_check_compiler_support(void) { #ifndef CC_USING_FENTRY diff --git a/arch/x86/kernel/livepatch.c b/arch/x86/kernel/livepatch.c index ff3c3101d..7a171c1 100644 --- a/arch/x86/kernel/livepatch.c +++ b/arch/x86/kernel/livepatch.c @@ -88,3 +88,8 @@ int klp_write_module_reloc(struct module *mod, unsigned long type, return ret; } + +unsigned long kgr_vmlinux_relocation_offset(void) +{ + return (unsigned long)&_text - __START_KERNEL; +} diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 284e269..5e85dde 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -234,8 +234,9 @@ static int klp_find_verify_func_addr(struct klp_object *obj, int ret; #if defined(CONFIG_RANDOMIZE_BASE) - /* KASLR is enabled, disregard old_addr from user */ - func->old_addr = 0; + /* If KASLR has been enabled, adjust old_addr accordingly */ + if (kaslr_enabled()) + func->old_addr += kgr_vmlinux_relocation_offset(); #endif if (!func->old_addr || klp_is_module(obj)) -- Jiri Kosina SUSE Labs -- 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/