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 65AC8C04A68 for ; Thu, 28 Jul 2022 11:49:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236719AbiG1Ltv (ORCPT ); Thu, 28 Jul 2022 07:49:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53774 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236167AbiG1Ltr (ORCPT ); Thu, 28 Jul 2022 07:49:47 -0400 Received: from mail-pj1-x1030.google.com (mail-pj1-x1030.google.com [IPv6:2607:f8b0:4864:20::1030]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 470C2691E1 for ; Thu, 28 Jul 2022 04:49:46 -0700 (PDT) Received: by mail-pj1-x1030.google.com with SMTP id pw15so1625697pjb.3 for ; Thu, 28 Jul 2022 04:49:46 -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=FuGo2hGCGa82jk275UGlQ/lMBHWW+gC0TJ/OSJFNVVg=; b=FTKOAJsOgk6g90cTCOXS+Q0GEu2Eh/zcFwc4Kl3pJny2BfESLuzfyKZcN4Sh+KfTD5 oTYH8gTgLno9nNaCmGySvu80n4iTRTArslvqls6yRLLW5CIUCXxfxeZyRKF5/5GOXMFi M2XiaesdcoWVKi33w2bh9QyR8cxY+QNSNufUGse+I8Us5zSfvx4fKKgePwvXprVXZecy 4Go9fu/YdhOgdRyY0VGLN17DRtIuP+XDds4Cjp6hrOUWTedVVJmJGSO4897NQOfqG9Ih yQ2V99H1NuLoNLNoK13w30v/fCGdJVs8HwjPru2BrBKZylJbjS5IW/5gfZ/HxvlJ7/gC 1UIg== 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=FuGo2hGCGa82jk275UGlQ/lMBHWW+gC0TJ/OSJFNVVg=; b=7SLkgwAAmMdcHe80X5IfaJYhwAsyuoheNDFl4ZV4ne8OIATZMsuQbks+wWwQsD6Oim UHgKvvzFQInDohNXc/gGX+J1xYna7sJRPRQVr4/9ge38HhndRL5kT6NltvEBoUlvS/Vf fFgaUjGg/vWXTJk4wCsUlcxJR3i+0CgT5IaqOVu8C83yb43eeo33JLaOUvv3ejiC+1bh gks2XK24sFURSG259dCvwcbRkL5u0feXkcN6rKTMHSMk8dE3ZJJLwckeQXSHF/aCvWWe OMo9s9NyTQ7uMKeKWi0vQNfNuje1auuTDAcNqblFY/0suLfV9wqmE0kZ0WJczigpYjhh +x4w== X-Gm-Message-State: AJIora9qn9Z17k6lhfifyHLRB1gjqmH5+UFgSRZo0vB40df11iRFdHX4 pC5NuS19CFSZEIzEBR06BijuFA== X-Google-Smtp-Source: AGRyM1vRx4Ytrd2vFeDMnd3OtaGgG6/z+Iwyu3C5PKp8GWsE/nyxpX848go4H8AyshSw+bjyqFsQ5w== X-Received: by 2002:a17:90b:1d12:b0:1f1:8d48:abaa with SMTP id on18-20020a17090b1d1200b001f18d48abaamr10158277pjb.96.1659008985827; Thu, 28 Jul 2022 04:49:45 -0700 (PDT) Received: from bogon.bytedance.net ([61.120.150.71]) by smtp.gmail.com with ESMTPSA id f4-20020a62db04000000b005251fc16ff8sm477419pfg.220.2022.07.28.04.49.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Jul 2022 04:49:45 -0700 (PDT) From: Jiachen Zhang To: miklos@szeredi.hu Cc: linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org, songmuchun@bytedance.com, Jiachen Zhang , Hongbo Yin , Tianci Zhang Subject: [PATCH v2] ovl: drop WARN_ON() dentry is NULL in ovl_encode_fh() Date: Thu, 28 Jul 2022 19:49:15 +0800 Message-Id: <20220728114915.91021-1-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 drop WARN_ON() 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..e065a5b9a442 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 (!dentry) return FILEID_INVALID; =20 bytes =3D ovl_dentry_to_fid(ofs, dentry, fid, buflen); --=20 2.20.1