From patchwork Fri Jun 25 20:04:52 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: 12345879 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=-19.1 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, 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 8CA97C49EA7 for ; Fri, 25 Jun 2021 20:05:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 720AD6195F for ; Fri, 25 Jun 2021 20:05:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229906AbhFYUHU (ORCPT ); Fri, 25 Jun 2021 16:07:20 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:48266 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S229878AbhFYUHS (ORCPT ); Fri, 25 Jun 2021 16:07:18 -0400 Received: from pps.filterd (m0089730.ppops.net [127.0.0.1]) by m0089730.ppops.net (8.16.0.43/8.16.0.43) with SMTP id 15PK4LAa001695 for ; Fri, 25 Jun 2021 13:04:56 -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=BCXA1is2SgfRbBG9IuoIHQcqTpKa0CM3/e/1g+2tH20=; b=TuTaZPWPpM9Ey4AEBjZ0j6/1t9cDjawfQdV5ECpbIxlSPoAGbKw12ItDUzcOp3VRXQ49 U19iCSA6yoK7/K652BApNjBQ+SOCGaGf9aMpOEV5TroBYQy/6abDt4N7olKj+9jvgKh8 tg5EF0DzUMyKbhiL8fTHX0ZrkmN65xlCXu0= Received: from maileast.thefacebook.com ([163.114.130.16]) by m0089730.ppops.net with ESMTP id 39d253xpe0-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 25 Jun 2021 13:04:56 -0700 Received: from intmgw001.05.ash9.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Fri, 25 Jun 2021 13:04:55 -0700 Received: by devbig005.ftw2.facebook.com (Postfix, from userid 6611) id 74D1E2942295; Fri, 25 Jun 2021 13:04:52 -0700 (PDT) From: Martin KaFai Lau To: CC: Alexei Starovoitov , Daniel Borkmann , Eric Dumazet , , Neal Cardwell , , Yonghong Song , Yuchung Cheng Subject: [PATCH bpf-next 1/8] tcp: seq_file: Avoid skipping sk during tcp_seek_last_pos Date: Fri, 25 Jun 2021 13:04:52 -0700 Message-ID: <20210625200452.723506-1-kafai@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210625200446.723230-1-kafai@fb.com> References: <20210625200446.723230-1-kafai@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-ORIG-GUID: LLQzaaBIou10o1ufzq1VNvrRI19U9Kpt X-Proofpoint-GUID: LLQzaaBIou10o1ufzq1VNvrRI19U9Kpt X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-06-25_07:2021-06-25,2021-06-25 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 priorityscore=1501 bulkscore=0 clxscore=1015 impostorscore=0 lowpriorityscore=0 adultscore=0 suspectscore=0 mlxlogscore=964 mlxscore=0 spamscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106250123 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") 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 6cb8e269f1ab..7a49427eefbf 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); }