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 2B13DC4332F for ; Wed, 9 Nov 2022 12:04:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229579AbiKIMEv (ORCPT ); Wed, 9 Nov 2022 07:04:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43094 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229447AbiKIMEt (ORCPT ); Wed, 9 Nov 2022 07:04:49 -0500 Received: from mail-pj1-x1031.google.com (mail-pj1-x1031.google.com [IPv6:2607:f8b0:4864:20::1031]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB1B82A726 for ; Wed, 9 Nov 2022 04:04:47 -0800 (PST) Received: by mail-pj1-x1031.google.com with SMTP id k5so16508924pjo.5 for ; Wed, 09 Nov 2022 04:04:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=P0s3cxJ3sHKa2IH5jImaelb3lptAzKadDfKWm7RrmSM=; b=0u+Y1bvrB+uIJ9r45t2leywA/j6CnxdI1J/xGQRyBrlkq3/VCcnwFR/8f2ibOZadFm 5uM539JlnXwUbiluDGLqvTSpy/ST1xSTyMbQ7so++YUpSb4TUsnrd9eWceowvzcgxx1Z htGJesNlZHDHg9hTP0Hf4HnvT3z/vyJpnTMMkn9NcwUIYqzIfTZMqjFtt2Zd9Mdvr4Y3 wmB3mRqs36bIrzRAt3Wwbym8nXv0ceyK5M9Wp/qqWU1bJZGRoj254ueThRqnkHSxikUL Io0sDALIzRZEW8gjrD4L+cO88bu8kf5P0M3QGnGxvRnCcDd33aA1jqW80vrPBDwKdo7o SjFg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=P0s3cxJ3sHKa2IH5jImaelb3lptAzKadDfKWm7RrmSM=; b=Bj3cG8iNxM9lVkrinD8NeXBj3Csvt+GcFNSW7o8OSI2V6k+Mh1crtFX7/yUnY7Jbrc +/2hAGP/vqwrQOnTgnoO63GZchfluVXB/G99BpFIzW5E+6wAzTi4Wjx/v/lTE1qvuO8D f0dPwKr+NiEQFY73a1ScZr29swXvdlCDi7Fqc3YFVYKdzFlsEVxxt7SP//KRrADD0ki/ vBsiOJOxWablKyO/1xfnLFG0V+ANV6TGBDQdtQjWklrJFZY87vx+fm6KV/JJIuXUrwVL x8MqXAsgdp9LxrKNMyky/GWnN6/J2L7DJM8/1maeDQYbYO75l6cQLGLQkZWvOXiF5ovf p0Nw== X-Gm-Message-State: ACrzQf36NicqweB/lfgWuOKT4EmNNOs0i7gA8VFr/oseDpGlfILrQB1P mIejrJPae9/glxxx7X+QF+53QQ== X-Google-Smtp-Source: AMsMyM6+yQNvNpRFLjzNuxSJuVgzbKZDHv9zB27pklJIi+LG2NXDhfnwxqFIhpwjxakNw2m3JyR4VQ== X-Received: by 2002:a17:903:264b:b0:186:af7a:391d with SMTP id je11-20020a170903264b00b00186af7a391dmr60835852plb.19.1667995487443; Wed, 09 Nov 2022 04:04:47 -0800 (PST) Received: from C02CV1DAMD6P.bytedance.net ([139.177.225.254]) by smtp.gmail.com with ESMTPSA id c195-20020a621ccc000000b00550724f8ea0sm8064581pfc.128.2022.11.09.04.04.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Nov 2022 04:04:46 -0800 (PST) From: Chengming Zhou To: gregkh@linuxfoundation.org, tj@kernel.org Cc: linux-kernel@vger.kernel.org, Chengming Zhou , syzbot+2fdf66e68f5f882c1074@syzkaller.appspotmail.com Subject: [PATCH] fs/kernfs: Fix lockdep warning in kernfs_active() Date: Wed, 9 Nov 2022 20:04:15 +0800 Message-Id: <20221109120415.55759-1-zhouchengming@bytedance.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <0000000000002473fd05eca7540a@google.com> References: <0000000000002473fd05eca7540a@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org syzbot found a lockdep warning in kernfs_find_and_get_node_by_id(), bisected to the commit c25491747b21 ("kernfs: Add KERNFS_REMOVING flags"), which didn't hold kernfs_rwsem before call kernfs_active(kn). Since kernfs_find_and_get_node_by_id() doesn't have to get active count of kn, only need to get a stable refcount of kn, so it should be enough to just check kn has been KERNFS_ACTIVATED. Reported-by: syzbot+2fdf66e68f5f882c1074@syzkaller.appspotmail.com Fixes: c25491747b21 ("kernfs: Add KERNFS_REMOVING flags") Signed-off-by: Chengming Zhou --- fs/kernfs/dir.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 6acd9c3d4cff..08f0f1570cd7 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -705,7 +705,13 @@ struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root, goto err_unlock; } - if (unlikely(!kernfs_active(kn) || !atomic_inc_not_zero(&kn->count))) + /* + * ACTIVATED is protected with kernfs_mutex but it was clear when + * @kn was added to idr and we just wanna see it set. No need to + * grab kernfs_mutex. + */ + if (unlikely(!(kn->flags & KERNFS_ACTIVATED) || + !atomic_inc_not_zero(&kn->count))) goto err_unlock; spin_unlock(&kernfs_idr_lock); -- 2.37.2