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[2620:137:e000::1:20]) by mx.google.com with ESMTP id j22-20020aa7ca56000000b004acb2ffd0dfsi12962656edt.412.2023.02.14.04.09.40; Tue, 14 Feb 2023 04:10:05 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@quicinc.com header.s=qcppdkim1 header.b=bHDwmNZq; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=quicinc.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229864AbjBNMHS (ORCPT + 99 others); Tue, 14 Feb 2023 07:07:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34762 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229742AbjBNMHQ (ORCPT ); Tue, 14 Feb 2023 07:07:16 -0500 Received: from mx0a-0031df01.pphosted.com (mx0a-0031df01.pphosted.com [205.220.168.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DECE66EA6; Tue, 14 Feb 2023 04:07:13 -0800 (PST) Received: from pps.filterd (m0279863.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 31E8MA2x018253; Tue, 14 Feb 2023 12:07:05 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; h=from : to : cc : subject : date : message-id : mime-version : content-type; s=qcppdkim1; bh=SRdv0mwY1mjW5CCdq+LWbNd2Y2xuZ8nNCpBpkpCRfC4=; b=bHDwmNZqAUKXonlnqLDL5cpq+CUCT+L2Ptr217SQUpYUYL6laVlrcNnIaIRZKxiSlqqW oz15yRXg7Z0eXqOOAeBeBaHu/gWzTLeYsJbIaJ3jnJy15CZY/RhsxIC0kJO/LRAW7hz8 Nma3K/NlE/R86zQEevPYVpqiLSRivI+Io4MhzKzVKhXjBrRGn55dZOMhVzqMzdPr/TQx zxTZ/rN56Ry4m7PSljQ2fks+YDLTcJwVLr7OJ/dVLeR1BHOfvjyaZ9HPQxsyrp6VaaEc 7Q2XpBBpkD1/ut7XItwDbncE8aTScijjTiuiTVm5uLO8fNWpdKFQekH4QmlvSywmYvTD Mg== Received: from nasanppmta03.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 3nr6ps0he4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 14 Feb 2023 12:07:04 +0000 Received: from nasanex01c.na.qualcomm.com (nasanex01c.na.qualcomm.com [10.45.79.139]) by NASANPPMTA03.qualcomm.com (8.17.1.5/8.17.1.5) with ESMTPS id 31EC744l022245 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 14 Feb 2023 12:07:04 GMT Received: from hu-mojha-hyd.qualcomm.com (10.80.80.8) by nasanex01c.na.qualcomm.com (10.45.79.139) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.36; Tue, 14 Feb 2023 04:07:01 -0800 From: Mukesh Ojha To: , CC: , , , , Mukesh Ojha Subject: [PATCH] ring-buffer: Handle race between rb_move_tail and rb_check_pages Date: Tue, 14 Feb 2023 17:36:43 +0530 Message-ID: <1676376403-16462-1-git-send-email-quic_mojha@quicinc.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01a.na.qualcomm.com (10.52.223.231) To nasanex01c.na.qualcomm.com (10.45.79.139) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: QhrLB9RCMbXZPuSs-i_ju3TxAF4X3P7P X-Proofpoint-GUID: QhrLB9RCMbXZPuSs-i_ju3TxAF4X3P7P X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.930,Hydra:6.0.562,FMLib:17.11.170.22 definitions=2023-02-14_07,2023-02-14_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 impostorscore=0 adultscore=0 mlxlogscore=978 malwarescore=0 priorityscore=1501 bulkscore=0 suspectscore=0 lowpriorityscore=0 mlxscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2302140105 X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1757808275422793019?= X-GMAIL-MSGID: =?utf-8?q?1757808275422793019?= It seems a data race between ring_buffer writing and integrity check. That is, RB_FLAG of head_page is been updating, while at same time RB_FLAG was cleared when doing integrity check rb_check_pages(): rb_check_pages() rb_handle_head_page(): -------- -------- rb_head_page_deactivate() rb_head_page_set_normal() rb_head_page_activate() We do intergrity test of the list to check if the list is corrupted and it is still worth doing it. So, let's refactor rb_check_pages() such that we no longer clear and set flag during the list sanity checking. [1] and [2] are the test to reproduce and the crash report respectively. 1: ``` read_trace.sh while true; do # the "trace" file is closed after read head -1 /sys/kernel/tracing/trace > /dev/null done ``` ``` repro.sh sysctl -w kernel.panic_on_warn=1 # function tracer will writing enough data into ring_buffer echo function > /sys/kernel/tracing/current_tracer ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ``` 2: ------------[ cut here ]------------ WARNING: CPU: 9 PID: 62 at kernel/trace/ring_buffer.c:2653 rb_move_tail+0x450/0x470 Modules linked in: CPU: 9 PID: 62 Comm: ksoftirqd/9 Tainted: G W 6.2.0-rc6+ Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014 RIP: 0010:rb_move_tail+0x450/0x470 Code: ff ff 4c 89 c8 f0 4d 0f b1 02 48 89 c2 48 83 e2 fc 49 39 d0 75 24 83 e0 03 83 f8 02 0f 84 e1 fb ff ff 48 8b 57 10 f0 ff 42 08 <0f> 0b 83 f8 02 0f 84 ce fb ff ff e9 db RSP: 0018:ffffb5564089bd00 EFLAGS: 00000203 RAX: 0000000000000000 RBX: ffff9db385a2bf81 RCX: ffffb5564089bd18 RDX: ffff9db281110100 RSI: 0000000000000fe4 RDI: ffff9db380145400 RBP: ffff9db385a2bf80 R08: ffff9db385a2bfc0 R09: ffff9db385a2bfc2 R10: ffff9db385a6c000 R11: ffff9db385a2bf80 R12: 0000000000000000 R13: 00000000000003e8 R14: ffff9db281110100 R15: ffffffffbb006108 FS: 0000000000000000(0000) GS:ffff9db3bdcc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005602323024c8 CR3: 0000000022e0c000 CR4: 00000000000006e0 Call Trace: ring_buffer_lock_reserve+0x136/0x360 ? __do_softirq+0x287/0x2df ? __pfx_rcu_softirq_qs+0x10/0x10 trace_function+0x21/0x110 ? __pfx_rcu_softirq_qs+0x10/0x10 ? __do_softirq+0x287/0x2df function_trace_call+0xf6/0x120 0xffffffffc038f097 ? rcu_softirq_qs+0x5/0x140 rcu_softirq_qs+0x5/0x140 __do_softirq+0x287/0x2df run_ksoftirqd+0x2a/0x30 smpboot_thread_fn+0x188/0x220 ? __pfx_smpboot_thread_fn+0x10/0x10 kthread+0xe7/0x110 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x2c/0x50 ---[ end trace 0000000000000000 ]--- [ crash report and test reproducer credit goes to Zheng Yejian] Reported-by: Zheng Yejian Signed-off-by: Mukesh Ojha --- kernel/trace/ring_buffer.c | 42 ++++++++++-------------------------------- 1 file changed, 10 insertions(+), 32 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index c366a0a..b641cab 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1581,19 +1581,6 @@ static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, } /** - * rb_check_list - make sure a pointer to a list has the last bits zero - */ -static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer, - struct list_head *list) -{ - if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev)) - return 1; - if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next)) - return 1; - return 0; -} - -/** * rb_check_pages - integrity check of buffer pages * @cpu_buffer: CPU buffer with pages to test * @@ -1602,36 +1589,27 @@ static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer, */ static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) { - struct list_head *head = cpu_buffer->pages; - struct buffer_page *bpage, *tmp; + struct list_head *head = rb_list_head(cpu_buffer->pages); + struct list_head *tmp; - /* Reset the head page if it exists */ - if (cpu_buffer->head_page) - rb_set_head_page(cpu_buffer); - - rb_head_page_deactivate(cpu_buffer); - - if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) - return -1; - if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) + if (RB_WARN_ON(cpu_buffer, + rb_list_head(rb_list_head(head->next)->prev) != head)) return -1; - if (rb_check_list(cpu_buffer, head)) + if (RB_WARN_ON(cpu_buffer, + rb_list_head(rb_list_head(head->prev)->next) != head)) return -1; - list_for_each_entry_safe(bpage, tmp, head, list) { + for (tmp = rb_list_head(head->next); tmp != head; tmp = rb_list_head(tmp->next)) { if (RB_WARN_ON(cpu_buffer, - bpage->list.next->prev != &bpage->list)) + rb_list_head(rb_list_head(tmp->next)->prev) != tmp)) return -1; + if (RB_WARN_ON(cpu_buffer, - bpage->list.prev->next != &bpage->list)) - return -1; - if (rb_check_list(cpu_buffer, &bpage->list)) + rb_list_head(rb_list_head(tmp->prev)->next) != tmp)) return -1; } - rb_head_page_activate(cpu_buffer); - return 0; }