From patchwork Tue Apr 12 06:30:31 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 560591 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 504DDC4167B for ; Tue, 12 Apr 2022 07:19:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351266AbiDLHVG (ORCPT ); Tue, 12 Apr 2022 03:21:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57746 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351823AbiDLHM7 (ORCPT ); Tue, 12 Apr 2022 03:12:59 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 39C4D17E0A; Mon, 11 Apr 2022 23:53:20 -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 ams.source.kernel.org (Postfix) with ESMTPS id E2C5EB81B46; Tue, 12 Apr 2022 06:53:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C501C385A1; Tue, 12 Apr 2022 06:53:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649746397; bh=3RUt2KxfRxSsYsWSSjP4U2KH/Rhc8qyzgbW8l/zg94U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xMJqyyHSVS+FGDqXAJt2FXwRN7a/hzhvWuKj+7aCbNO2VYS+vzUeuEgMBNrSogD8w /vZjibZ6VOazQNWGF8sMYqoudHw7l+xePeQYnYe6rrfkGX3n/reNqPhp5uDO1OnDYv g+IdDGnK3LbBKizSlTovq4HkzknvzK8KXW3u+rrY= 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 5.15 228/277] arm64: patch_text: Fixup last cpu should be master Date: Tue, 12 Apr 2022 08:30:31 +0200 Message-Id: <20220412062948.643072909@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220412062942.022903016@linuxfoundation.org> References: <20220412062942.022903016@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 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/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]);