From patchwork Mon Jul 12 06:08:11 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 474568 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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, 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 51C61C07E9B for ; Mon, 12 Jul 2021 06:19:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3E781610E6 for ; Mon, 12 Jul 2021 06:19:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234561AbhGLGW3 (ORCPT ); Mon, 12 Jul 2021 02:22:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:39904 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234210AbhGLGVX (ORCPT ); Mon, 12 Jul 2021 02:21:23 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 86AFF610E5; Mon, 12 Jul 2021 06:18:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626070713; bh=dAnvGLufU6Ejd9Nv5NgVmc7qe7BYvQ/94+7Rvi8+U/8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RM4kECN+1BX7/XlRjoMLrb73Qau8rwju1fZG1qdJlj7fRRwg6G7bIMy88KbXIjmkG l1gXDwyy8ybfRNDmqAoXdcUtiLNdDApGV+NpaISs2lGYq6EK3ndLLIOZcdEBQ5GO7n C7z2lLrfi2MCtyDT4u15Qt3iaUULmqexkfbCPpsQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Johannes Berg , Boqun Feng , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 5.4 107/348] lockding/lockdep: Avoid to find wrong lock dep path in check_irq_usage() Date: Mon, 12 Jul 2021 08:08:11 +0200 Message-Id: <20210712060715.767577496@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060659.886176320@linuxfoundation.org> References: <20210712060659.886176320@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Boqun Feng [ Upstream commit 7b1f8c6179769af6ffa055e1169610b51d71edd5 ] In the step #3 of check_irq_usage(), we seach backwards to find a lock whose usage conflicts the usage of @target_entry1 on safe/unsafe. However, we should only keep the irq-unsafe usage of @target_entry1 into consideration, because it could be a case where a lock is hardirq-unsafe but soft-safe, and in check_irq_usage() we find it because its hardirq-unsafe could result into a hardirq-safe-unsafe deadlock, but currently since we don't filter out the other usage bits, so we may find a lock dependency path softirq-unsafe -> softirq-safe, which in fact doesn't cause a deadlock. And this may cause misleading lockdep splats. Fix this by only keeping LOCKF_ENABLED_IRQ_ALL bits when we try the backwards search. Reported-by: Johannes Berg Signed-off-by: Boqun Feng Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210618170110.3699115-4-boqun.feng@gmail.com Signed-off-by: Sasha Levin --- kernel/locking/lockdep.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index df43bf53e7c5..3ec8fd2e80e5 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -2377,8 +2377,18 @@ static int check_irq_usage(struct task_struct *curr, struct held_lock *prev, * Step 3: we found a bad match! Now retrieve a lock from the backward * list whose usage mask matches the exclusive usage mask from the * lock found on the forward list. + * + * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering + * the follow case: + * + * When trying to add A -> B to the graph, we find that there is a + * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M, + * that B -> ... -> M. However M is **softirq-safe**, if we use exact + * invert bits of M's usage_mask, we will find another lock N that is + * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not + * cause a inversion deadlock. */ - backward_mask = original_mask(target_entry1->class->usage_mask); + backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL); ret = find_usage_backwards(&this, backward_mask, &target_entry); if (ret < 0) {