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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 236C9C433F5 for ; Mon, 18 Apr 2022 14:14:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343500AbiDRORA (ORCPT ); Mon, 18 Apr 2022 10:17:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36556 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343911AbiDROPv (ORCPT ); Mon, 18 Apr 2022 10:15:51 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A897D393D2; Mon, 18 Apr 2022 06:12:41 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6F90160F9E; Mon, 18 Apr 2022 13:12:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 67393C385A1; Mon, 18 Apr 2022 13:12:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1650287551; bh=mVo4UmQIIjFD79mpgLYNeOvHMT7O3IVl7jFF4a7Vh44=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1tOUx6HeqOgctR28sZrinOj2eAXYMV5EFxn9JP3wmBWmHS+eD19Sm8ahmr3Esqwa4 Cl13UBvIHckxkpZ8eUj7M02JlXMovLMM6kmxZrLZeBw8VhioYxVAi91rR6C9FrlaqE VF/S2IiyvmTOhvrNcas5lmlO5vemCK3S4ppcnfCs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Guo Ren , Guo Ren , Catalin Marinas , Masami Hiramatsu , Will Deacon Subject: [PATCH 4.9 196/218] arm64: patch_text: Fixup last cpu should be master Date: Mon, 18 Apr 2022 14:14:22 +0200 Message-Id: <20220418121207.133915106@linuxfoundation.org> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20220418121158.636999985@linuxfoundation.org> References: <20220418121158.636999985@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Guo Ren commit 31a099dbd91e69fcab55eef4be15ed7a8c984918 upstream. These patch_text implementations are using stop_machine_cpuslocked infrastructure with atomic cpu_count. The original idea: When the master CPU patch_text, the others should wait for it. But current implementation is using the first CPU as master, which couldn't guarantee the remaining CPUs are waiting. This patch changes the last CPU as the master to solve the potential risk. Fixes: ae16480785de ("arm64: introduce interfaces to hotpatch kernel and module code") Signed-off-by: Guo Ren Signed-off-by: Guo Ren Reviewed-by: Catalin Marinas Reviewed-by: Masami Hiramatsu Cc: Link: https://lore.kernel.org/r/20220407073323.743224-2-guoren@kernel.org Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/insn.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/arm64/kernel/insn.c +++ b/arch/arm64/kernel/insn.c @@ -234,8 +234,8 @@ static int __kprobes aarch64_insn_patch_ int i, ret = 0; struct aarch64_insn_patch *pp = arg; - /* The first CPU becomes master */ - if (atomic_inc_return(&pp->cpu_count) == 1) { + /* The last CPU becomes master */ + if (atomic_inc_return(&pp->cpu_count) == num_online_cpus()) { for (i = 0; ret == 0 && i < pp->insn_cnt; i++) ret = aarch64_insn_patch_text_nosync(pp->text_addrs[i], pp->new_insns[i]);