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 01926C35296 for ; Tue, 12 Apr 2022 09:07:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1387295AbiDLJGk (ORCPT ); Tue, 12 Apr 2022 05:06:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57654 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1359138AbiDLHmd (ORCPT ); Tue, 12 Apr 2022 03:42:33 -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 84F3229C9A; Tue, 12 Apr 2022 00:20:20 -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 2017C616B2; Tue, 12 Apr 2022 07:20:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2B716C385A5; Tue, 12 Apr 2022 07:20:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649748019; bh=3RUt2KxfRxSsYsWSSjP4U2KH/Rhc8qyzgbW8l/zg94U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VWTOMeKdRFTvk5q9m8o9rGAHltTix9wp6zXC7dT+qeU9BjzFbPxmepPBv0wXcxfsy 70q9cB4QIbdX8l9A5bknZFF9XYYAyvi99Uvve9rPzPywXy8yBdZfGMxCLKBfaJA2PH rTN9YdCV9c9LaKbxkrNOvEifpZd6WbiMc9DXqwFA= 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 5.17 291/343] arm64: patch_text: Fixup last cpu should be master Date: Tue, 12 Apr 2022 08:31:49 +0200 Message-Id: <20220412062959.727297612@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220412062951.095765152@linuxfoundation.org> References: <20220412062951.095765152@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: linux-kernel@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/patching.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/arm64/kernel/patching.c +++ b/arch/arm64/kernel/patching.c @@ -117,8 +117,8 @@ 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]);