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=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, 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 B1C74C10F14 for ; Thu, 10 Oct 2019 06:19:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8917E2190F for ; Thu, 10 Oct 2019 06:19:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="VpkPzN+N" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726973AbfJJGTa (ORCPT ); Thu, 10 Oct 2019 02:19:30 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:24066 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732898AbfJJGT3 (ORCPT ); Thu, 10 Oct 2019 02:19:29 -0400 Received: from pps.filterd (m0001303.ppops.net [127.0.0.1]) by m0001303.ppops.net (8.16.0.42/8.16.0.42) with SMTP id x9A6Cbai018650 for ; Wed, 9 Oct 2019 23:19:28 -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-type; s=facebook; bh=H5WTiUKRu1qDnKEKpnXoZ0t4lsxmbyz/pzW2AERatVE=; b=VpkPzN+N6TbLnGIfa7Olee2m9RdSMucn9U+I2oiVTekSQbCyQ5wis9JddYAkR1fPojUb cy7qygFYDBAjDzV4Di6+f0vKBhllNkDo7MLAtwhqnEAC7xEoedOz7A/R5uiaeIGMpZ1j +QqPwR5xladfgZJRAZ2ac1IldxAZOhxgqQk= Received: from mail.thefacebook.com (mailout.thefacebook.com [199.201.64.23]) by m0001303.ppops.net with ESMTP id 2vgr0gtmgk-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NOT) for ; Wed, 09 Oct 2019 23:19:28 -0700 Received: from 2401:db00:2050:5076:face:0:9:0 (2620:10d:c081:10::13) by mail.thefacebook.com (2620:10d:c081:35::125) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA) id 15.1.1713.5; Wed, 9 Oct 2019 23:19:26 -0700 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id F369962E3559; Wed, 9 Oct 2019 23:19:24 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Song Liu Smtp-Origin-Hostname: devbig006.ftw2.facebook.com To: , , CC: , Song Liu , , Peter Zijlstra , Alexei Starovoitov , Daniel Borkmann Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH bpf-next 2/2] bpf/stackmap: fix A-A deadlock in bpf_get_stack() Date: Wed, 9 Oct 2019 23:19:16 -0700 Message-ID: <20191010061916.198761-3-songliubraving@fb.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191010061916.198761-1-songliubraving@fb.com> References: <20191010061916.198761-1-songliubraving@fb.com> X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,1.0.8 definitions=2019-10-10_03:2019-10-08,2019-10-10 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 clxscore=1015 bulkscore=0 priorityscore=1501 impostorscore=0 mlxscore=0 spamscore=0 malwarescore=0 suspectscore=2 adultscore=0 lowpriorityscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1908290000 definitions=main-1910100058 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org bpf stackmap with build-id lookup (BPF_F_STACK_BUILD_ID) can trigger A-A deadlock on rq_lock(): rcu: INFO: rcu_sched detected stalls on CPUs/tasks: [...] Call Trace: try_to_wake_up+0x1ad/0x590 wake_up_q+0x54/0x80 rwsem_wake+0x8a/0xb0 bpf_get_stack+0x13c/0x150 bpf_prog_fbdaf42eded9fe46_on_event+0x5e3/0x1000 bpf_overflow_handler+0x60/0x100 __perf_event_overflow+0x4f/0xf0 perf_swevent_overflow+0x99/0xc0 ___perf_sw_event+0xe7/0x120 __schedule+0x47d/0x620 schedule+0x29/0x90 futex_wait_queue_me+0xb9/0x110 futex_wait+0x139/0x230 do_futex+0x2ac/0xa50 __x64_sys_futex+0x13c/0x180 do_syscall_64+0x42/0x100 entry_SYSCALL_64_after_hwframe+0x44/0xa9 This can be reproduced by: 1. Start a multi-thread program that does parallel mmap() and malloc(); 2. taskset the program to 2 CPUs; 3. Attach bpf program to trace_sched_switch and gather stackmap with build-id, e.g. with trace.py from bcc tools: trace.py -U -p -s t:sched:sched_switch A sample reproducer is attached at the end. Fix this by checking whether rq_lock is already locked. If so, postpone the up_read() to irq_work, just like the in_nmi() case. Fixes: commit 615755a77b24 ("bpf: extend stackmap to save binary_build_id+offset instead of address") Cc: stable@vger.kernel.org # v4.17+ Cc: Peter Zijlstra Cc: Alexei Starovoitov Cc: Daniel Borkmann Reported-by: Tejun Heo Signed-off-by: Song Liu Reproducer: ============================ 8< ============================ char *filename; void *worker(void *p) { void *ptr; int fd; char *pptr; fd = open(filename, O_RDONLY); if (fd < 0) return NULL; while (1) { struct timespec ts = {0, 1000 + rand() % 2000}; ptr = mmap(NULL, 4096 * 64, PROT_READ, MAP_PRIVATE, fd, 0); usleep(1); if (ptr == MAP_FAILED) { printf("failed to mmap\n"); break; } munmap(ptr, 4096 * 64); usleep(1); pptr = malloc(1); usleep(1); pptr[0] = 1; usleep(1); free(pptr); usleep(1); nanosleep(&ts, NULL); } close(fd); return NULL; } int main(int argc, char *argv[]) { void *ptr; int i; pthread_t threads[THREAD_COUNT]; if (argc < 2) return 0; filename = argv[1]; for (i = 0; i < THREAD_COUNT; i++) { if (pthread_create(threads + i, NULL, worker, NULL)) { fprintf(stderr, "Error creating thread\n"); return 0; } } for (i = 0; i < THREAD_COUNT; i++) pthread_join(threads[i], NULL); return 0; } ============================ 8< ============================ --- kernel/bpf/stackmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 052580c33d26..3b278f6b0c3e 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -287,7 +287,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, bool irq_work_busy = false; struct stack_map_irq_work *work = NULL; - if (in_nmi()) { + if (in_nmi() || this_rq_is_locked()) { work = this_cpu_ptr(&up_read_work); if (work->irq_work.flags & IRQ_WORK_BUSY) /* cannot queue more up_read, fallback */ -- 2.17.1