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 49FD4C49EC6 for ; Tue, 23 Aug 2022 10:32:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355367AbiHWKbu (ORCPT ); Tue, 23 Aug 2022 06:31:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54550 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353717AbiHWKPr (ORCPT ); Tue, 23 Aug 2022 06:15:47 -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 1199974343; Tue, 23 Aug 2022 02:00:54 -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 208D2B81C1C; Tue, 23 Aug 2022 09:00:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6AF57C433C1; Tue, 23 Aug 2022 09:00:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661245251; bh=NWppDAppclIIelcwHTi7iypa3FSdoMiyO4BC8w4uwr0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JPSpM8u6rAACmaLvjKqFAp9nCwcLFfzcRaIJoza+4kNitAzTq/u9AgpOvS7JgSG54 se/LTz79YSu/Llb2RVlYeXccStOjWyhNpFlsV3XxLOBhZri1ywfFU9B6jD6PKvqJlz MQNLksJmhzBMDoNL2z2Y74El7m8+fIwGXU3GAzV0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hongbo Yin , Jiachen Zhang , Tianci Zhang , Miklos Szeredi Subject: [PATCH 4.19 020/287] ovl: drop WARN_ON() dentry is NULL in ovl_encode_fh() Date: Tue, 23 Aug 2022 10:23:09 +0200 Message-Id: <20220823080100.961392451@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080100.268827165@linuxfoundation.org> References: <20220823080100.268827165@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jiachen Zhang commit dd524b7f317de8d31d638cbfdc7be4cf9b770e42 upstream. 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 Fixes: 8ed5eec9d6c4 ("ovl: encode pure upper file handles") Cc: # v4.16 Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman --- fs/overlayfs/export.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -277,7 +277,7 @@ static int ovl_encode_fh(struct inode *i return FILEID_INVALID; dentry = d_find_any_alias(inode); - if (WARN_ON(!dentry)) + if (!dentry) return FILEID_INVALID; type = ovl_dentry_to_fh(dentry, fid, max_len);