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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B406C32771 for ; Fri, 19 Aug 2022 21:08:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 431FA6B0073; Fri, 19 Aug 2022 17:08:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3BAED6B0074; Fri, 19 Aug 2022 17:08:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 25B1B8D0002; Fri, 19 Aug 2022 17:08:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 12B046B0073 for ; Fri, 19 Aug 2022 17:08:14 -0400 (EDT) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id D2D28161B23 for ; Fri, 19 Aug 2022 21:08:13 +0000 (UTC) X-FDA: 79817580066.15.25BB468 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf06.hostedemail.com (Postfix) with ESMTP id 6996C18000E for ; Fri, 19 Aug 2022 21:08:13 +0000 (UTC) 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 09252B80B9E; Fri, 19 Aug 2022 21:08:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 90D9BC433D7; Fri, 19 Aug 2022 21:08:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1660943290; bh=6yIJjHS2JZBDcDI1TurkDjj2O3UtwWKh20HdULweR4U=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=diIKdZLzUlo2DYSfAH2kJuTr8tm9cdXOAq+DtCll6fsyBEXMv3Tne+eoICil/9SmT zXpwvGvq6TITh8Oyt4fo3IIUcjyf6wAxIZf0El6D1GBFq/OdeZrSiN4usL/tC/Zguk rfjHnGw4XKMtUloaM5zqtw02/H+K8N566lER4Ilc= Date: Fri, 19 Aug 2022 14:08:09 -0700 From: Andrew Morton To: SeongJae Park Cc: badari.pulavarty@intel.com, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] mm/damon/dbgfs: avoid duplicate context directory creation Message-Id: <20220819140809.1e3929fd8f50bfc32cae31d3@linux-foundation.org> In-Reply-To: <20220819171930.16166-1-sj@kernel.org> References: <20220819171930.16166-1-sj@kernel.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660943293; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=0luMyY8JarDhCGKUqkW/HmMUxG8g4uorOMXdgPSTCnY=; b=6eBi481Y2+XpvskpRAP7mX+fmIHvitrnAUpdNrm64+KKqk6lKRujusxzJW3m+hJUQIK749 hCnCvYqYm0xf1JVKCJM0Ct9eG5chmUACa86P33SqZathsc8a3HDAUsrL+H0KVLAdgT2EBW NftFr1n/xKUp3Kz83xP37PEQtZGOmHU= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=diIKdZLz; dmarc=none; spf=pass (imf06.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660943293; a=rsa-sha256; cv=none; b=5jLWlhvIoCa/aNdurmXwayivb8jfbUJ0jod1nP6f8aceONmN+evoj8a1DBWPySkFv0g+PQ Lso4xvqn4tzjbiIkngkMxbbGITmPJfdYWZoSjT4g2E8jq8Zl+Oqck3llcXWpBSUAIM/4u1 Wbm7WsGyTi55adKcqQZN7OSPz/aOl6c= Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=diIKdZLz; dmarc=none; spf=pass (imf06.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 6996C18000E X-Stat-Signature: 1beo1iq9esyuh98kzgpsem3somiak53i X-Rspam-User: X-HE-Tag: 1660943293-389552 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 19 Aug 2022 17:19:30 +0000 SeongJae Park wrote: > From: Badari Pulavarty > > When user tries to create a DAMON context via the DAMON debugfs > interface with a name of an already existing context, the context > directory creation silently fails but the context is added in the > internal data structure. As a result, memory could leak and DAMON > cannot be turned on. An example test case is as below: > > # cd /sys/kernel/debug/damon/ > # echo "off" > monitor_on > # echo paddr > target_ids > # echo "abc" > mk_context > # echo "abc" > mk_context > # echo $$ > abc/target_ids > # echo "on" > monitor_on <<< fails > > This commit fixes the issue by checking if the name already exist and > immediately returning '-EEXIST' in the case. > > ... > > --- a/mm/damon/dbgfs.c > +++ b/mm/damon/dbgfs.c > @@ -795,7 +795,7 @@ static void dbgfs_destroy_ctx(struct damon_ctx *ctx) > */ > static int dbgfs_mk_context(char *name) > { > - struct dentry *root, **new_dirs, *new_dir; > + struct dentry *root, **new_dirs, *new_dir, *dir; > struct damon_ctx **new_ctxs, *new_ctx; > > if (damon_nr_running_ctxs()) > @@ -817,6 +817,12 @@ static int dbgfs_mk_context(char *name) > if (!root) > return -ENOENT; > > + dir = debugfs_lookup(name, root); > + if (dir) { > + dput(dir); > + return -EEXIST; > + } > + > new_dir = debugfs_create_dir(name, root); > dbgfs_dirs[dbgfs_nr_ctxs] = new_dir; It would be simpler (and less racy) to check the debugfs_create_dir() return value for IS_ERR()?