From patchwork Mon Oct 24 11:29:41 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 8765 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:6687:0:0:0:0:0 with SMTP id l7csp430398wru; Mon, 24 Oct 2022 05:41:26 -0700 (PDT) X-Google-Smtp-Source: AMsMyM6g19euwsbsdhG1CGk+gYLlU9FEYANIu+i/S96gRX2PoxV9fsiSrmxXJh8zK0lb5pJVuPwE X-Received: by 2002:a17:907:a042:b0:7a0:3323:2883 with SMTP id gz2-20020a170907a04200b007a033232883mr11182712ejc.37.1666615286158; Mon, 24 Oct 2022 05:41:26 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1666615286; cv=none; d=google.com; s=arc-20160816; b=A80KiJuQ02uHyngh076WuNRDwlAz4fx1fzpWQbXvoyG6/VDBdxjIcKWfjk9oUmrhKe bsacjOM6YoR2QKHEbzV8aHpItkYSLQE+eazQwle3VEXj8AfVAqyqxCxa52WNKmHb/5Cq M37bcooFT0zFEba8l7V/jaztAS9Ab3NFQBsPU1hgd3bhvRj9JsPplabLkswqHXhWBUL6 Ab4U/Q9dmviDvwDGjkaE6T/jOmc7kjFQ0DuS88KvJ+cGNFgbLlefTrgESos51z8kL2wA MgtrJf6Dn04vnXy5cWJtxmxtBVX1YwnqnpuwktMfBapVPGXylqkV99RQWMj8L3Bgm7Ej VXDQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :user-agent:references:in-reply-to:message-id:date:subject:cc:to :from:dkim-signature; bh=WjYu/qj3SHo5TEhVA6nx3g98ala4gKfbtrsFROwNt1o=; b=gJqRnIxiJQY6yXW+PyiAtODXrnFNYGDGSFCXebuEzd1M3PPz6XpG8Qtw6y/BjwPxqf gI0CE65igRKOHhKRJnxEGxsBzX/5mDmFEyAgg/1OF2o2X1ZgUvNG/KBTNIy8MusOapQD +RPDwoBVCUPHiAhz+J98T6G9VHPHx+xozeo3VEVA4y5FHHO9137tFiH+hMdzZ85lNBOB AGWtQb00tCNOCh3RNN4md06RzE0ibR6Y+ZFK9ZAavISph4qUEfKgiMYJ+hVzJrm/4q1N zaNFczveDi7iPLB0TV2145FP+sBvFUJgN7CIzbLV23QGrLz1ewWercwxHdfTjcp/3ZB+ v5RQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linuxfoundation.org header.s=korg header.b="Evv2zQ/k"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linuxfoundation.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id y26-20020aa7d51a000000b00461a7962c26si3483209edq.527.2022.10.24.05.41.00; Mon, 24 Oct 2022 05:41:26 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linuxfoundation.org header.s=korg header.b="Evv2zQ/k"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linuxfoundation.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233741AbiJXM2y (ORCPT + 99 others); Mon, 24 Oct 2022 08:28:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57948 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233719AbiJXM1t (ORCPT ); Mon, 24 Oct 2022 08:27:49 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C2C3886803; Mon, 24 Oct 2022 05:01:40 -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 B81E1B811EF; Mon, 24 Oct 2022 11:57:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 12EA7C433C1; Mon, 24 Oct 2022 11:57:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666612635; bh=Krt+Xlxa8gyzGMZVPSaqFF395LKyxhWwJdymKAbkvjA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Evv2zQ/knYl47KuNTrqnJ44UiLUQjTGUtEhjJfDcEV/5D2mHFDMOw+xcLKxfjKSkS qYF/3Bdk88cWpiTmNeCjJrdBNMzWWEZOFvBlNyD+rLVdRBJvpax+6jNTVAMnMbDX1w hfM36JsuzCXUKxTgvcAsPqjq82bSOn1oLJKSZ6s4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Rik van Riel , Breno Leitao , Petr Mladek , Josh Poimboeuf , stable@kernel.org Subject: [PATCH 4.19 062/229] livepatch: fix race between fork and KLP transition Date: Mon, 24 Oct 2022 13:29:41 +0200 Message-Id: <20221024113001.087187890@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221024112959.085534368@linuxfoundation.org> References: <20221024112959.085534368@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 X-Spam-Status: No, score=-7.6 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747572789959710723?= X-GMAIL-MSGID: =?utf-8?q?1747572789959710723?= From: Rik van Riel commit 747f7a2901174c9afa805dddfb7b24db6f65e985 upstream. The KLP transition code depends on the TIF_PATCH_PENDING and the task->patch_state to stay in sync. On a normal (forward) transition, TIF_PATCH_PENDING will be set on every task in the system, while on a reverse transition (after a failed forward one) first TIF_PATCH_PENDING will be cleared from every task, followed by it being set on tasks that need to be transitioned back to the original code. However, the fork code copies over the TIF_PATCH_PENDING flag from the parent to the child early on, in dup_task_struct and setup_thread_stack. Much later, klp_copy_process will set child->patch_state to match that of the parent. However, the parent's patch_state may have been changed by KLP loading or unloading since it was initially copied over into the child. This results in the KLP code occasionally hitting this warning in klp_complete_transition: for_each_process_thread(g, task) { WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING)); task->patch_state = KLP_UNDEFINED; } Set, or clear, the TIF_PATCH_PENDING flag in the child task depending on whether or not it is needed at the time klp_copy_process is called, at a point in copy_process where the tasklist_lock is held exclusively, preventing races with the KLP code. The KLP code does have a few places where the state is changed without the tasklist_lock held, but those should not cause problems because klp_update_patch_state(current) cannot be called while the current task is in the middle of fork, klp_check_and_switch_task() which is called under the pi_lock, which prevents rescheduling, and manipulation of the patch state of idle tasks, which do not fork. This should prevent this warning from triggering again in the future, and close the race for both normal and reverse transitions. Signed-off-by: Rik van Riel Reported-by: Breno Leitao Reviewed-by: Petr Mladek Acked-by: Josh Poimboeuf Fixes: d83a7cb375ee ("livepatch: change to a per-task consistency model") Cc: stable@kernel.org Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20220808150019.03d6a67b@imladris.surriel.com Signed-off-by: Greg Kroah-Hartman --- kernel/livepatch/transition.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) --- a/kernel/livepatch/transition.c +++ b/kernel/livepatch/transition.c @@ -563,9 +563,23 @@ void klp_reverse_transition(void) /* Called from copy_process() during fork */ void klp_copy_process(struct task_struct *child) { - child->patch_state = current->patch_state; - /* TIF_PATCH_PENDING gets copied in setup_thread_stack() */ + /* + * The parent process may have gone through a KLP transition since + * the thread flag was copied in setup_thread_stack earlier. Bring + * the task flag up to date with the parent here. + * + * The operation is serialized against all klp_*_transition() + * operations by the tasklist_lock. The only exception is + * klp_update_patch_state(current), but we cannot race with + * that because we are current. + */ + if (test_tsk_thread_flag(current, TIF_PATCH_PENDING)) + set_tsk_thread_flag(child, TIF_PATCH_PENDING); + else + clear_tsk_thread_flag(child, TIF_PATCH_PENDING); + + child->patch_state = current->patch_state; } /*