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[209.132.180.67]) by mx.google.com with ESMTP id b35si4531790edb.204.2019.10.18.09.13.28; Fri, 18 Oct 2019 09:13:51 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2439798AbfJQODe (ORCPT + 99 others); Thu, 17 Oct 2019 10:03:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39264 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727542AbfJQODe (ORCPT ); Thu, 17 Oct 2019 10:03:34 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9815B65F7B; Thu, 17 Oct 2019 14:03:32 +0000 (UTC) Received: from localhost (unknown [10.36.118.91]) by smtp.corp.redhat.com (Postfix) with ESMTP id C4CD060C5D; Thu, 17 Oct 2019 14:03:31 +0000 (UTC) Date: Thu, 17 Oct 2019 15:03:30 +0100 From: "Richard W.M. Jones" To: Mike Christie Cc: syzbot , axboe@kernel.dk, josef@toxicpanda.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, nbd@other.debian.org, syzkaller-bugs@googlegroups.com Subject: Re: INFO: task hung in nbd_ioctl Message-ID: <20191017140330.GB25667@redhat.com> References: <000000000000b1b1ee0593cce78f@google.com> <5D93C2DD.10103@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5D93C2DD.10103@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Thu, 17 Oct 2019 14:03:32 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 01, 2019 at 04:19:25PM -0500, Mike Christie wrote: > Hey Josef and nbd list, > > I had a question about if there are any socket family restrictions for nbd? In normal circumstances, in userspace, the NBD protocol would only be used over AF_UNIX or AF_INET/AF_INET6. There's a bit of confusion because netlink is used by nbd-client to configure the NBD device, setting things like block size and timeouts (instead of ioctl which is deprecated). I think you don't mean this use of netlink? > The bug here is that some socket familys do not support the > sock->ops->shutdown callout, and when nbd calls kernel_sock_shutdown > their callout returns -EOPNOTSUPP. That then leaves recv_work stuck in > nbd_read_stat -> sock_xmit -> sock_recvmsg. My patch added a > flush_workqueue call, so for socket familys like AF_NETLINK in this bug > we hang like we see below. > > I can just remove the flush_workqueue call in that code path since it's > not needed there, but it leaves the original bug my patch was hitting > where we leave the recv_work running which can then result in leaked > resources, or possible use after free crashes and you still get the hang > if you remove the module. > > It looks like we have used kernel_sock_shutdown for a while so I thought > we might never have supported sockets that did not support the callout. > Is that correct? If so then I can just add a check for this in > nbd_add_socket and fix that bug too. Rich. > On 09/30/2019 05:39 PM, syzbot wrote: > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: bb2aee77 Add linux-next specific files for 20190926 > > git tree: linux-next > > console output: https://syzkaller.appspot.com/x/log.txt?x=13385ca3600000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=e60af4ac5a01e964 > > dashboard link: > > https://syzkaller.appspot.com/bug?extid=24c12fa8d218ed26011a > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12abc2a3600000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11712c05600000 > > > > The bug was bisected to: > > > > commit e9e006f5fcf2bab59149cb38a48a4817c1b538b4 > > Author: Mike Christie > > Date: Sun Aug 4 19:10:06 2019 +0000 > > > > nbd: fix max number of supported devs > > > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1226f3c5600000 > > final crash: https://syzkaller.appspot.com/x/report.txt?x=1126f3c5600000 > > console output: https://syzkaller.appspot.com/x/log.txt?x=1626f3c5600000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+24c12fa8d218ed26011a@syzkaller.appspotmail.com > > Fixes: e9e006f5fcf2 ("nbd: fix max number of supported devs") > > > > INFO: task syz-executor390:8778 can't die for more than 143 seconds. > > syz-executor390 D27432 8778 8777 0x00004004 > > Call Trace: > > context_switch kernel/sched/core.c:3384 [inline] > > __schedule+0x828/0x1c20 kernel/sched/core.c:4065 > > schedule+0xd9/0x260 kernel/sched/core.c:4132 > > schedule_timeout+0x717/0xc50 kernel/time/timer.c:1871 > > do_wait_for_common kernel/sched/completion.c:83 [inline] > > __wait_for_common kernel/sched/completion.c:104 [inline] > > wait_for_common kernel/sched/completion.c:115 [inline] > > wait_for_completion+0x29c/0x440 kernel/sched/completion.c:136 > > flush_workqueue+0x40f/0x14c0 kernel/workqueue.c:2826 > > nbd_start_device_ioctl drivers/block/nbd.c:1272 [inline] > > __nbd_ioctl drivers/block/nbd.c:1347 [inline] > > nbd_ioctl+0xb2e/0xc44 drivers/block/nbd.c:1387 > > __blkdev_driver_ioctl block/ioctl.c:304 [inline] > > blkdev_ioctl+0xedb/0x1c20 block/ioctl.c:606 > > block_ioctl+0xee/0x130 fs/block_dev.c:1954 > > vfs_ioctl fs/ioctl.c:47 [inline] > > file_ioctl fs/ioctl.c:539 [inline] > > do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:726 > > ksys_ioctl+0xab/0xd0 fs/ioctl.c:743 > > __do_sys_ioctl fs/ioctl.c:750 [inline] > > __se_sys_ioctl fs/ioctl.c:748 [inline] > > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:748 > > do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > RIP: 0033:0x4452d9 > > Code: Bad RIP value. > > RSP: 002b:00007ffde928d288 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004452d9 > > RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000004 > > RBP: 0000000000000000 R08: 00000000004025b0 R09: 00000000004025b0 > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402520 > > R13: 00000000004025b0 R14: 0000000000000000 R15: 0000000000000000 > > INFO: task syz-executor390:8778 blocked for more than 143 seconds. > > Not tainted 5.3.0-next-20190926 #0 > > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > syz-executor390 D27432 8778 8777 0x00004004 > > Call Trace: > > context_switch kernel/sched/core.c:3384 [inline] > > __schedule+0x828/0x1c20 kernel/sched/core.c:4065 > > schedule+0xd9/0x260 kernel/sched/core.c:4132 > > schedule_timeout+0x717/0xc50 kernel/time/timer.c:1871 > > do_wait_for_common kernel/sched/completion.c:83 [inline] > > __wait_for_common kernel/sched/completion.c:104 [inline] > > wait_for_common kernel/sched/completion.c:115 [inline] > > wait_for_completion+0x29c/0x440 kernel/sched/completion.c:136 > > flush_workqueue+0x40f/0x14c0 kernel/workqueue.c:2826 > > nbd_start_device_ioctl drivers/block/nbd.c:1272 [inline] > > __nbd_ioctl drivers/block/nbd.c:1347 [inline] > > nbd_ioctl+0xb2e/0xc44 drivers/block/nbd.c:1387 > > __blkdev_driver_ioctl block/ioctl.c:304 [inline] > > blkdev_ioctl+0xedb/0x1c20 block/ioctl.c:606 > > block_ioctl+0xee/0x130 fs/block_dev.c:1954 > > vfs_ioctl fs/ioctl.c:47 [inline] > > file_ioctl fs/ioctl.c:539 [inline] > > do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:726 > > ksys_ioctl+0xab/0xd0 fs/ioctl.c:743 > > __do_sys_ioctl fs/ioctl.c:750 [inline] > > __se_sys_ioctl fs/ioctl.c:748 [inline] > > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:748 > > do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > RIP: 0033:0x4452d9 > > Code: Bad RIP value. > > RSP: 002b:00007ffde928d288 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004452d9 > > RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000004 > > RBP: 0000000000000000 R08: 00000000004025b0 R09: 00000000004025b0 > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402520 > > R13: 00000000004025b0 R14: 0000000000000000 R15: 0000000000000000 > > > > Showing all locks held in the system: > > 1 lock held by khungtaskd/1066: > > #0: ffffffff88faad80 (rcu_read_lock){....}, at: > > debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:5337 > > 2 locks held by kworker/u5:0/1525: > > #0: ffff8880923d0d28 ((wq_completion)knbd0-recv){+.+.}, at: > > __write_once_size include/linux/compiler.h:226 [inline] > > #0: ffff8880923d0d28 ((wq_completion)knbd0-recv){+.+.}, at: > > arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] > > #0: ffff8880923d0d28 ((wq_completion)knbd0-recv){+.+.}, at: > > atomic64_set include/asm-generic/atomic-instrumented.h:855 [inline] > > #0: ffff8880923d0d28 ((wq_completion)knbd0-recv){+.+.}, at: > > atomic_long_set include/asm-generic/atomic-long.h:40 [inline] > > #0: ffff8880923d0d28 ((wq_completion)knbd0-recv){+.+.}, at: > > set_work_data kernel/workqueue.c:620 [inline] > > #0: ffff8880923d0d28 ((wq_completion)knbd0-recv){+.+.}, at: > > set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline] > > #0: ffff8880923d0d28 ((wq_completion)knbd0-recv){+.+.}, at: > > process_one_work+0x88b/0x1740 kernel/workqueue.c:2240 > > #1: ffff8880a63b7dc0 ((work_completion)(&args->work)){+.+.}, at: > > process_one_work+0x8c1/0x1740 kernel/workqueue.c:2244 > > 1 lock held by rsyslogd/8659: > > 2 locks held by getty/8749: > > #0: ffff888098c08090 (&tty->ldisc_sem){++++}, at: > > ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 > > #1: ffffc90005f112e0 (&ldata->atomic_read_lock){+.+.}, at: > > n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156 > > 2 locks held by getty/8750: > > #0: ffff88808f10b090 (&tty->ldisc_sem){++++}, at: > > ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 > > #1: ffffc90005f2d2e0 (&ldata->atomic_read_lock){+.+.}, at: > > n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156 > > 2 locks held by getty/8751: > > #0: ffff88809a6be090 (&tty->ldisc_sem){++++}, at: > > ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 > > #1: ffffc90005f192e0 (&ldata->atomic_read_lock){+.+.}, at: > > n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156 > > 2 locks held by getty/8752: > > #0: ffff8880a48af090 (&tty->ldisc_sem){++++}, at: > > ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 > > #1: ffffc90005f352e0 (&ldata->atomic_read_lock){+.+.}, at: > > n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156 > > 2 locks held by getty/8753: > > #0: ffff88808c599090 (&tty->ldisc_sem){++++}, at: > > ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 > > #1: ffffc90005f212e0 (&ldata->atomic_read_lock){+.+.}, at: > > n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156 > > 2 locks held by getty/8754: > > #0: ffff88808f1a8090 (&tty->ldisc_sem){++++}, at: > > ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 > > #1: ffffc90005f392e0 (&ldata->atomic_read_lock){+.+.}, at: > > n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156 > > 2 locks held by getty/8755: > > #0: ffff88809ab33090 (&tty->ldisc_sem){++++}, at: > > ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 > > #1: ffffc90005f012e0 (&ldata->atomic_read_lock){+.+.}, at: > > n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156 > > > > ============================================= > > > > NMI backtrace for cpu 1 > > CPU: 1 PID: 1066 Comm: khungtaskd Not tainted 5.3.0-next-20190926 #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > > Google 01/01/2011 > > Call Trace: > > __dump_stack lib/dump_stack.c:77 [inline] > > dump_stack+0x172/0x1f0 lib/dump_stack.c:113 > > nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101 > > nmi_trigger_cpumask_backtrace+0x23b/0x28b lib/nmi_backtrace.c:62 > > arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 > > trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] > > check_hung_uninterruptible_tasks kernel/hung_task.c:269 [inline] > > watchdog+0xc99/0x1360 kernel/hung_task.c:353 > > kthread+0x361/0x430 kernel/kthread.c:255 > > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 > > Sending NMI from CPU 1 to CPUs 0: > > NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0xe/0x10 > > arch/x86/include/asm/irqflags.h:60 > > > > > > --- > > This bug is generated by a bot. It may contain errors. > > See https://goo.gl/tpsmEJ for more information about syzbot. > > syzbot engineers can be reached at syzkaller@googlegroups.com. > > > > syzbot will keep track of this bug report. See: > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > For information about bisection process see: > > https://goo.gl/tpsmEJ#bisection > > syzbot can test patches for this bug, for details see: > > https://goo.gl/tpsmEJ#testing-patches -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW