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 X-Spam-Level: X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 53FAFC4332F for ; Mon, 13 Sep 2021 14:29:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 41DF960F44 for ; Mon, 13 Sep 2021 14:29:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245039AbhIMObC (ORCPT ); Mon, 13 Sep 2021 10:31:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:51248 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346413AbhIMO2q (ORCPT ); Mon, 13 Sep 2021 10:28:46 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3041561B93; Mon, 13 Sep 2021 13:50:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1631541014; bh=xS9WL+Fre7/1R/6UqIqDuJp4qna4GDASzkCwcd8Scb4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kNrb6o22RRoXFeLOETsD63knNNGxrqJzCTIdIef73JgUrLlsEVhaoLBuU4Ajad+ye 5l/MT9cJZrbA8sYgQjDUBKy50jlcEbcwlF9kULPuWJ7TGN50dwN6wB9myw8AnnXXCS pxhOXnHehPmhRn9T/XoQDiiRkotjiKwpGEV07IC0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Martin KaFai Lau , Andrii Nakryiko , Eric Dumazet , Kuniyuki Iwashima , Yonghong Song , Sasha Levin Subject: [PATCH 5.14 126/334] tcp: seq_file: Avoid skipping sk during tcp_seek_last_pos Date: Mon, 13 Sep 2021 15:13:00 +0200 Message-Id: <20210913131117.627037049@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210913131113.390368911@linuxfoundation.org> References: <20210913131113.390368911@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Martin KaFai Lau [ Upstream commit 525e2f9fd0229eb10cb460a9e6d978257f24804e ] st->bucket stores the current bucket number. st->offset stores the offset within this bucket that is the sk to be seq_show(). Thus, st->offset only makes sense within the same st->bucket. These two variables are an optimization for the common no-lseek case. When resuming the seq_file iteration (i.e. seq_start()), tcp_seek_last_pos() tries to continue from the st->offset at bucket st->bucket. However, it is possible that the bucket pointed by st->bucket has changed and st->offset may end up skipping the whole st->bucket without finding a sk. In this case, tcp_seek_last_pos() currently continues to satisfy the offset condition in the next (and incorrect) bucket. Instead, regardless of the offset value, the first sk of the next bucket should be returned. Thus, "bucket == st->bucket" check is added to tcp_seek_last_pos(). The chance of hitting this is small and the issue is a decade old, so targeting for the next tree. Fixes: a8b690f98baf ("tcp: Fix slowness in read /proc/net/tcp") Signed-off-by: Martin KaFai Lau Signed-off-by: Andrii Nakryiko Reviewed-by: Eric Dumazet Acked-by: Kuniyuki Iwashima Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20210701200541.1033917-1-kafai@fb.com Signed-off-by: Sasha Levin --- net/ipv4/tcp_ipv4.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index a692626c19e4..db07c05736b2 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -2451,6 +2451,7 @@ static void *tcp_get_idx(struct seq_file *seq, loff_t pos) static void *tcp_seek_last_pos(struct seq_file *seq) { struct tcp_iter_state *st = seq->private; + int bucket = st->bucket; int offset = st->offset; int orig_num = st->num; void *rc = NULL; @@ -2461,7 +2462,7 @@ static void *tcp_seek_last_pos(struct seq_file *seq) break; st->state = TCP_SEQ_STATE_LISTENING; rc = listening_get_next(seq, NULL); - while (offset-- && rc) + while (offset-- && rc && bucket == st->bucket) rc = listening_get_next(seq, rc); if (rc) break; @@ -2472,7 +2473,7 @@ static void *tcp_seek_last_pos(struct seq_file *seq) if (st->bucket > tcp_hashinfo.ehash_mask) break; rc = established_get_first(seq); - while (offset-- && rc) + while (offset-- && rc && bucket == st->bucket) rc = established_get_next(seq, rc); } -- 2.30.2