From patchwork Mon Oct 5 15:26:52 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 290594 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6C09C46466 for ; Mon, 5 Oct 2020 15:42:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 896E22075A for ; Mon, 5 Oct 2020 15:42:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601912564; bh=dd5UUlSboBzKgMHvCLv4sN0FrjygQhRfX13+YSVt78g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=gpMTyBkJEjUW3enmtNsmnjO7IAU+d8rAA0xmp4qGSWYLi9g69kcrmf8sO6eUMDTQc UDvHNQ/H3NJv1g5iVCzmn1aK6wNptedb9pxPQMKNVSP+2isbvvhsMaikmEo9GUTUJC lQOX13J9OrEjZ9IPcj8q3tebyj4WM80lT/3GL7/M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728485AbgJEPmd (ORCPT ); Mon, 5 Oct 2020 11:42:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:52818 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727320AbgJEP2B (ORCPT ); Mon, 5 Oct 2020 11:28:01 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 04C772100A; Mon, 5 Oct 2020 15:27:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601911680; bh=dd5UUlSboBzKgMHvCLv4sN0FrjygQhRfX13+YSVt78g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mJEjVCE14ruQB9Zrq1zCOBv7ksW+6fMj+UuXWv/8oZ5MYLsKPsYAkCSBjrEv5stsx HNEgn6miDj/DtcO6URPdwssTePNyYChzLU2t0tbM5AK1eHCEm01/EvtuXFY2DgJfjH DPJaIuORWWSvpLANiYODntx0xhQF0DW9Amel/p8M= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro Subject: [PATCH 4.19 35/38] epoll: replace ->visited/visited_list with generation count Date: Mon, 5 Oct 2020 17:26:52 +0200 Message-Id: <20201005142110.370567345@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201005142108.650363140@linuxfoundation.org> References: <20201005142108.650363140@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Al Viro commit 18306c404abe18a0972587a6266830583c60c928 upstream. removes the need to clear it, along with the races. Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- fs/eventpoll.c | 26 +++++++------------------- 1 file changed, 7 insertions(+), 19 deletions(-) --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -222,8 +222,7 @@ struct eventpoll { struct file *file; /* used to optimize loop detection check */ - int visited; - struct list_head visited_list_link; + u64 gen; #ifdef CONFIG_NET_RX_BUSY_POLL /* used to track busy poll napi_id */ @@ -273,6 +272,8 @@ static long max_user_watches __read_most */ static DEFINE_MUTEX(epmutex); +static u64 loop_check_gen = 0; + /* Used to check for epoll file descriptor inclusion loops */ static struct nested_calls poll_loop_ncalls; @@ -282,9 +283,6 @@ static struct kmem_cache *epi_cache __re /* Slab cache used to allocate "struct eppoll_entry" */ static struct kmem_cache *pwq_cache __read_mostly; -/* Visited nodes during ep_loop_check(), so we can unset them when we finish */ -static LIST_HEAD(visited_list); - /* * List of files with newly added links, where we may need to limit the number * of emanating paths. Protected by the epmutex. @@ -1867,13 +1865,12 @@ static int ep_loop_check_proc(void *priv struct epitem *epi; mutex_lock_nested(&ep->mtx, call_nests + 1); - ep->visited = 1; - list_add(&ep->visited_list_link, &visited_list); + ep->gen = loop_check_gen; for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) { epi = rb_entry(rbp, struct epitem, rbn); if (unlikely(is_file_epoll(epi->ffd.file))) { ep_tovisit = epi->ffd.file->private_data; - if (ep_tovisit->visited) + if (ep_tovisit->gen == loop_check_gen) continue; error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, ep_loop_check_proc, epi->ffd.file, @@ -1914,18 +1911,8 @@ static int ep_loop_check_proc(void *priv */ static int ep_loop_check(struct eventpoll *ep, struct file *file) { - int ret; - struct eventpoll *ep_cur, *ep_next; - - ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, + return ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, ep_loop_check_proc, file, ep, current); - /* clear visited list */ - list_for_each_entry_safe(ep_cur, ep_next, &visited_list, - visited_list_link) { - ep_cur->visited = 0; - list_del(&ep_cur->visited_list_link); - } - return ret; } static void clear_tfile_check_list(void) @@ -2147,6 +2134,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, in error_tgt_fput: if (full_check) { clear_tfile_check_list(); + loop_check_gen++; mutex_unlock(&epmutex); }