From patchwork Thu Jul 1 20:05:41 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin KaFai Lau X-Patchwork-Id: 12354753 X-Patchwork-Delegate: bpf@iogearbox.net 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=-19.2 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, 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 6507BC11F64 for ; Thu, 1 Jul 2021 20:05:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 46D8261411 for ; Thu, 1 Jul 2021 20:05:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229894AbhGAUIS (ORCPT ); Thu, 1 Jul 2021 16:08:18 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:41158 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233491AbhGAUIR (ORCPT ); Thu, 1 Jul 2021 16:08:17 -0400 Received: from pps.filterd (m0109334.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 161Jwjv5001206 for ; Thu, 1 Jul 2021 13:05:46 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=4JzmU94JfPnQkwQ4bDUq+83XjyG3dTzA3zR1RCB4Jbw=; b=gtPkXTJCNkbTcpgKTZn5NfUGJly2QljUUcqF7bz7p0PBf0388mi7KXWALEBsJbPA0nFw 1xdVqmkeGIUPDKhTA9oGpMx0o8e1vcmAoMXwaZoYMuUzH+Tsv/WmGDAxX56HYPsRX8hL 0f40URaAhOwOoeGuKFqCmPXb6qJgYYQkBu0= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 39h1wyxbr6-6 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 01 Jul 2021 13:05:46 -0700 Received: from intmgw001.06.ash9.facebook.com (2620:10d:c085:108::4) by mail.thefacebook.com (2620:10d:c085:11d::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 1 Jul 2021 13:05:44 -0700 Received: by devbig005.ftw2.facebook.com (Postfix, from userid 6611) id DAC172940BB9; Thu, 1 Jul 2021 13:05:41 -0700 (PDT) From: Martin KaFai Lau To: CC: Alexei Starovoitov , Daniel Borkmann , Eric Dumazet , , Neal Cardwell , , Yonghong Song , Yuchung Cheng Subject: [PATCH v2 bpf-next 1/8] tcp: seq_file: Avoid skipping sk during tcp_seek_last_pos Date: Thu, 1 Jul 2021 13:05:41 -0700 Message-ID: <20210701200541.1033917-1-kafai@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210701200535.1033513-1-kafai@fb.com> References: <20210701200535.1033513-1-kafai@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-ORIG-GUID: XW5Pq3lWGJv6qGlkL23OJrKfzsBTemJq X-Proofpoint-GUID: XW5Pq3lWGJv6qGlkL23OJrKfzsBTemJq X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-07-01_12:2021-07-01,2021-07-01 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 impostorscore=0 mlxscore=0 lowpriorityscore=0 malwarescore=0 bulkscore=0 clxscore=1015 priorityscore=1501 spamscore=0 mlxlogscore=958 suspectscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107010117 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net 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") Acked-by: Yonghong Song Signed-off-by: Martin KaFai Lau --- 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 e66ad6bfe808..26b7b2056585 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); }