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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 701D8C433EF for ; Fri, 1 Jul 2022 09:08:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235571AbiGAJIo (ORCPT ); Fri, 1 Jul 2022 05:08:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52856 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232948AbiGAJIl (ORCPT ); Fri, 1 Jul 2022 05:08:41 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B1161EC62 for ; Fri, 1 Jul 2022 02:08:37 -0700 (PDT) Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.56]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4LZ8Sn2d6Mz1L8Vl; Fri, 1 Jul 2022 17:06:17 +0800 (CST) Received: from kwepemm600003.china.huawei.com (7.193.23.202) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 1 Jul 2022 17:08:36 +0800 Received: from [10.67.111.205] (10.67.111.205) by kwepemm600003.china.huawei.com (7.193.23.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 1 Jul 2022 17:08:35 +0800 From: Yang Jihong Subject: [BUG] I found a syzkaller softlockup "BUG: soft lockup in __mmap_region" To: , linux-kernel , "Ingo Molnar" CC: Message-ID: <7c67bae9-be74-e3cc-9189-e42bbb39a0a0@huawei.com> Date: Fri, 1 Jul 2022 17:08:34 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.111.205] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemm600003.china.huawei.com (7.193.23.202) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello， In my environment, a perf_mmap softlockup syzkaller problem occurs. The call stack is as follows: [ 3666.984385][ C2] watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [syz-executor.2:32404] [ 3666.986137][ C2] Modules linked in: [ 3666.989581][ C2] CPU: 2 PID: 32404 Comm: syz-executor.2 Not tainted 5.10.0+ #4 [ 3666.990697][ C2] Hardware name: linux,dummy-virt (DT) [ 3666.992270][ C2] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=--) [ 3666.993787][ C2] pc : __kasan_check_write+0x0/0x40 [ 3666.994841][ C2] lr : perf_mmap+0x3c8/0xf80 [ 3666.995661][ C2] sp : ffff00001011f8f0 [ 3666.996598][ C2] x29: ffff00001011f8f0 x28: ffff0000cf644868 [ 3666.998488][ C2] x27: ffff000012cad2c0 x26: 0000000000000000 [ 3666.999888][ C2] x25: 0000000000000001 x24: ffff000012cad298 [ 3667.003511][ C2] x23: 0000000000000000 x22: ffff000012cad000 [ 3667.005504][ C2] x21: ffff0000cf644818 x20: ffff0000cf6d2400 [ 3667.006891][ C2] x19: ffff0000cf6d24c0 x18: 0000000000000000 [ 3667.008295][ C2] x17: 0000000000000000 x16: 0000000000000000 [ 3667.009528][ C2] x15: 0000000000000000 x14: 0000000000000000 [ 3667.010658][ C2] x13: 0000000000000000 x12: ffff800002023f17 [ 3667.012169][ C2] x11: 1fffe00002023f16 x10: ffff800002023f16 [ 3667.013780][ C2] x9 : dfffa00000000000 x8 : ffff00001011f8b7 [ 3667.015265][ C2] x7 : 0000000000000001 x6 : ffff800002023f16 [ 3667.016683][ C2] x5 : ffff0000c0f36400 x4 : 0000000000000000 [ 3667.018078][ C2] x3 : ffffa00010000000 x2 : ffffa000119a0000 [ 3667.019343][ C2] x1 : 0000000000000004 x0 : ffff0000cf6d24c0 [ 3667.021276][ C2] Call trace: [ 3667.022598][ C2] __kasan_check_write+0x0/0x40 [ 3667.023666][ C2] __mmap_region+0x7a4/0xc90 [ 3667.024679][ C2] __do_mmap_mm+0x600/0xa20 [ 3667.025700][ C2] do_mmap+0x114/0x384 [ 3667.026583][ C2] vm_mmap_pgoff+0x138/0x230 [ 3667.027532][ C2] ksys_mmap_pgoff+0x1d8/0x570 [ 3667.028537][ C2] __arm64_sys_mmap+0xa4/0xd0 [ 3667.029597][ C2] el0_svc_common.constprop.0+0xf4/0x414 [ 3667.030682][ C2] do_el0_svc+0x50/0x11c [ 3667.031545][ C2] el0_svc+0x20/0x30 [ 3667.032368][ C2] el0_sync_handler+0xe4/0x1e0 [ 3667.033305][ C2] el0_sync+0x148/0x180 I checked the perf_mmap code locally. When the problem occurred, the kernel kept running the goto again command: again: mutex_lock(&event->mmap_mutex); if (event->rb) { if (data_page_nr(event->rb) != nr_pages) { ret = -EINVAL; goto unlock; } if (!atomic_inc_not_zero(&event->rb->mmap_count)) { /* * Raced against perf_mmap_close() through * perf_event_set_output(). Try again, hope for bette * luck. */ mutex_unlock(&event->mmap_mutex); goto again; ===> kept goto again } goto unlock; } else { printk("[%d]test_mmap: perf_mmap lock, NULL\n", get_cpu()); put_cpu(); } Under what conditions would this cause? Best Regards, Yang