From nobody Wed Apr 15 01:31:11 2026 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 53634C04A68 for ; Thu, 28 Jul 2022 06:40:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233783AbiG1GkB (ORCPT ); Thu, 28 Jul 2022 02:40:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44658 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233614AbiG1Gj6 (ORCPT ); Thu, 28 Jul 2022 02:39:58 -0400 Received: from mail-pf1-x42e.google.com (mail-pf1-x42e.google.com [IPv6:2607:f8b0:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3AEC5C96F for ; Wed, 27 Jul 2022 23:39:57 -0700 (PDT) Received: by mail-pf1-x42e.google.com with SMTP id b133so1120951pfb.6 for ; Wed, 27 Jul 2022 23:39:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=/kUZ/dgqC7iw0jhI4uYoWyAcN87LUuqF13JYqIaofqY=; b=hTxJbdtJd14HVPheUaqfh98GeNpnBo3mzEF73RKAoFpp+jNZuDAMxRDyKMNSidAYur lWqQY/766U1A1JtH3lOY4TzIlJXpOZenWrAFHJlgNMpROvL18TdxgfISIWp3i0Ywll1j j6Z+uq/2+NlpnaVM63F+yyb7MYeXg4cwVh15kC0KXxVuPbV5KknP7MNMI1WDeXvG45rR 72LX1ZOOVRsD0BMe7cAsrhhUMMk8ZoMQYwXKiBkLEwJ+93Ypmw/TCotxWMZMN0kv949x Zwxy8sNaYe3oo40Hkzj5VQScEIgTDYo5hgUPhoLcawI+BU+Yzad3YwEPD0tcsne7Nkwv ArRw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=/kUZ/dgqC7iw0jhI4uYoWyAcN87LUuqF13JYqIaofqY=; b=sbg7O671XTrcdit889lEirlRIThRPrOfOzbbzLjY7LPcyhsaDEE7Lz4AMqgw5sverC sIc4wc6kZqeEYzD8gJGh88MtUjthm78qAwoW3SMsKnq6fDj/MixiPc45hAIi1PdQXckr 6n2wNfX9Fa46Ok5yl4fascMHL+cgYJdPiqwCcCqJ9H4H1oP7xpaMxP8A6IxtADfbrqL/ rYO1ys3950QsuYeGwKnWKPSVVeNTrpnYaGxD+Iuf0tREEeIYRKGu954JZXlFRs5+k4z/ gHq5XSWj39aMVyoLdnGOBtwXy2KWI0chArpCvpv6sA+LBfDccrXa4S/IFbvCq1Tv731U Egwg== X-Gm-Message-State: AJIora97iKkZNJ+CaLBpn77kQQCtiCmC9sQk4kR/gkXGAcqU3xrdEWc5 rmZq6HNCf6AXhw7MZAJz/lQzTA== X-Google-Smtp-Source: AGRyM1tvBFvRXWWgx31iR7pfQeXgyc4b1FfwvZgr1t5Z3xxZ5QUrFkoWWUhy4aMXTTZ+7pxYqOhPQg== X-Received: by 2002:a65:57c6:0:b0:415:c329:5d49 with SMTP id q6-20020a6557c6000000b00415c3295d49mr21175206pgr.581.1658990397120; Wed, 27 Jul 2022 23:39:57 -0700 (PDT) Received: from localhost.localdomain ([61.120.150.71]) by smtp.gmail.com with ESMTPSA id l1-20020a17090a384100b001f31e91200asm704723pjf.44.2022.07.27.23.39.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Jul 2022 23:39:56 -0700 (PDT) From: Jiachen Zhang To: miklos@szeredi.hu Cc: linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org, Jiachen Zhang , Hongbo Yin , Tianci Zhang Subject: [PATCH] ovl: only WARN_ON_ONCE() if dentry is NULL in ovl_encode_fh() Date: Thu, 28 Jul 2022 14:38:55 +0800 Message-Id: <20220728063856.72705-1-zhangjiachen.jaycee@bytedance.com> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Some code paths cannot guarantee the inode have any dentry alias. So WARN_ON() all !dentry may flood the kernel logs. For example, when an overlayfs inode is watched by inotifywait (1), and someone is trying to read the /proc/$(pidof inotifywait)/fdinfo/INOTIFY_FD, at that time if the dentry has been reclaimed by kernel (such as echo 2 > /proc/sys/vm/drop_caches), there will be a WARN_ON(). The printed call stack would be like: ? show_mark_fhandle+0xf0/0xf0 show_mark_fhandle+0x4a/0xf0 ? show_mark_fhandle+0xf0/0xf0 ? seq_vprintf+0x30/0x50 ? seq_printf+0x53/0x70 ? show_mark_fhandle+0xf0/0xf0 inotify_fdinfo+0x70/0x90 show_fdinfo.isra.4+0x53/0x70 seq_show+0x130/0x170 seq_read+0x153/0x440 vfs_read+0x94/0x150 ksys_read+0x5f/0xe0 do_syscall_64+0x59/0x1e0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 So let's replace WARN_ON() with WARN_ON_ONCE() to avoid kernel log flooding. Reported-by: Hongbo Yin Signed-off-by: Jiachen Zhang Signed-off-by: Tianci Zhang --- fs/overlayfs/export.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c index 2eada97bbd23..3a8650442aec 100644 --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -259,7 +259,7 @@ static int ovl_encode_fh(struct inode *inode, u32 *fid,= int *max_len, return FILEID_INVALID; =20 dentry =3D d_find_any_alias(inode); - if (WARN_ON(!dentry)) + if (WARN_ON_ONCE(!dentry)) return FILEID_INVALID; =20 bytes =3D ovl_dentry_to_fid(ofs, dentry, fid, buflen); --=20 2.20.1