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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 E1F26C433F5 for ; Sun, 2 Sep 2018 17:34:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A67EE20843 for ; Sun, 2 Sep 2018 17:34:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A67EE20843 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=vmware.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726999AbeIBVuO (ORCPT ); Sun, 2 Sep 2018 17:50:14 -0400 Received: from ex13-edg-ou-002.vmware.com ([208.91.0.190]:36915 "EHLO EX13-EDG-OU-002.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726065AbeIBVuN (ORCPT ); Sun, 2 Sep 2018 17:50:13 -0400 Received: from sc9-mailhost3.vmware.com (10.113.161.73) by EX13-EDG-OU-002.vmware.com (10.113.208.156) with Microsoft SMTP Server id 15.0.1156.6; Sun, 2 Sep 2018 10:33:40 -0700 Received: from sc2-haas01-esx0118.eng.vmware.com (sc2-haas01-esx0118.eng.vmware.com [10.172.44.118]) by sc9-mailhost3.vmware.com (Postfix) with ESMTP id B4F1540713; Sun, 2 Sep 2018 10:33:42 -0700 (PDT) From: Nadav Amit To: Thomas Gleixner CC: , Ingo Molnar , , Arnd Bergmann , , Dave Hansen , Nadav Amit , Nadav Amit , Jiri Kosina , Andy Lutomirski , Kees Cook , Dave Hansen Subject: [PATCH v2 1/6] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()" Date: Sun, 2 Sep 2018 10:32:19 -0700 Message-ID: <20180902173224.30606-2-namit@vmware.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180902173224.30606-1-namit@vmware.com> References: <20180902173224.30606-1-namit@vmware.com> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: None (EX13-EDG-OU-002.vmware.com: namit@vmware.com does not designate permitted sender hosts) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org text_mutex is expected to be held before text_poke() is called, but we cannot add a lockdep assertion since kgdb does not take it, and instead *supposedly* ensures the lock is not taken and will not be acquired by any other core while text_poke() is running. The reason for the "supposedly" comment is that it is not entirely clear that this would be the case if gdb_do_roundup is zero. Add a comment to clarify this behavior, and restore the assertions as they were before the recent commit. This partially reverts commit 9222f606506c ("x86/alternatives: Lockdep-enforce text_mutex in text_poke*()") Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Kees Cook Cc: Dave Hansen Fixes: 9222f606506c ("x86/alternatives: Lockdep-enforce text_mutex in text_poke*()") Reviewed-by: Masami Hiramatsu Tested-by: Masami Hiramatsu Suggested-by: Peter Zijlstra Signed-off-by: Nadav Amit --- arch/x86/kernel/alternative.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index b9d5e7c9ef43..e9be18245698 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -684,6 +684,11 @@ void *__init_or_module text_poke_early(void *addr, const void *opcode, * It means the size must be writable atomically and the address must be aligned * in a way that permits an atomic write. It also makes sure we fit on a single * page. + * + * Context: Must be called under text_mutex. kgdb is an exception: it does not + * hold the mutex, as it *supposedly* ensures that no other core is + * holding the mutex and ensures that none of them will acquire the + * mutex while the code runs. */ void *text_poke(void *addr, const void *opcode, size_t len) { @@ -698,8 +703,6 @@ void *text_poke(void *addr, const void *opcode, size_t len) */ BUG_ON(!after_bootmem); - lockdep_assert_held(&text_mutex); - if (!core_kernel_text((unsigned long)addr)) { pages[0] = vmalloc_to_page(addr); pages[1] = vmalloc_to_page(addr + PAGE_SIZE); -- 2.17.1 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nadav Amit Subject: [PATCH v2 1/6] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()" Date: Sun, 2 Sep 2018 10:32:19 -0700 Message-ID: <20180902173224.30606-2-namit@vmware.com> References: <20180902173224.30606-1-namit@vmware.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <20180902173224.30606-1-namit@vmware.com> Sender: linux-kernel-owner@vger.kernel.org To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, Ingo Molnar , x86@kernel.org, Arnd Bergmann , linux-arch@vger.kernel.org, Dave Hansen , Nadav Amit , Nadav Amit , Jiri Kosina , Andy Lutomirski , Kees Cook , Dave Hansen List-Id: linux-arch.vger.kernel.org text_mutex is expected to be held before text_poke() is called, but we cannot add a lockdep assertion since kgdb does not take it, and instead *supposedly* ensures the lock is not taken and will not be acquired by any other core while text_poke() is running. The reason for the "supposedly" comment is that it is not entirely clear that this would be the case if gdb_do_roundup is zero. Add a comment to clarify this behavior, and restore the assertions as they were before the recent commit. This partially reverts commit 9222f606506c ("x86/alternatives: Lockdep-enforce text_mutex in text_poke*()") Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Kees Cook Cc: Dave Hansen Fixes: 9222f606506c ("x86/alternatives: Lockdep-enforce text_mutex in text_poke*()") Reviewed-by: Masami Hiramatsu Tested-by: Masami Hiramatsu Suggested-by: Peter Zijlstra Signed-off-by: Nadav Amit --- arch/x86/kernel/alternative.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index b9d5e7c9ef43..e9be18245698 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -684,6 +684,11 @@ void *__init_or_module text_poke_early(void *addr, const void *opcode, * It means the size must be writable atomically and the address must be aligned * in a way that permits an atomic write. It also makes sure we fit on a single * page. + * + * Context: Must be called under text_mutex. kgdb is an exception: it does not + * hold the mutex, as it *supposedly* ensures that no other core is + * holding the mutex and ensures that none of them will acquire the + * mutex while the code runs. */ void *text_poke(void *addr, const void *opcode, size_t len) { @@ -698,8 +703,6 @@ void *text_poke(void *addr, const void *opcode, size_t len) */ BUG_ON(!after_bootmem); - lockdep_assert_held(&text_mutex); - if (!core_kernel_text((unsigned long)addr)) { pages[0] = vmalloc_to_page(addr); pages[1] = vmalloc_to_page(addr + PAGE_SIZE); -- 2.17.1