INFO: task hung in nbd_ioctl (2)

From: syzbot
Date: Mon Jul 06 2020 - 11:22:38 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1124dead100000
kernel config: https://syzkaller.appspot.com/x/.config?x=d195fe572fb15312
dashboard link: https://syzkaller.appspot.com/bug?extid=e36f41d207137b5d12f7
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e36f41d207137b5d12f7@xxxxxxxxxxxxxxxxxxxxxxxxx

INFO: task syz-executor.1:13143 blocked for more than 143 seconds.
Not tainted 5.7.0-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1 D27616 13143 6943 0x00004004
Call Trace:
context_switch kernel/sched/core.c:3430 [inline]
__schedule+0x8f3/0x1fc0 kernel/sched/core.c:4156
schedule+0xd0/0x2a0 kernel/sched/core.c:4231
schedule_timeout+0x55b/0x850 kernel/time/timer.c:1873
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x16a/0x270 kernel/sched/completion.c:138
flush_workqueue+0x403/0x14f0 kernel/workqueue.c:2831
nbd_start_device_ioctl drivers/block/nbd.c:1322 [inline]
__nbd_ioctl drivers/block/nbd.c:1397 [inline]
nbd_ioctl+0x7ae/0xb7f drivers/block/nbd.c:1437
__blkdev_driver_ioctl block/ioctl.c:224 [inline]
blkdev_ioctl+0x25e/0x6c0 block/ioctl.c:620
block_ioctl+0xf9/0x140 fs/block_dev.c:1987
vfs_ioctl fs/ioctl.c:47 [inline]
ksys_ioctl+0x11a/0x180 fs/ioctl.c:771
__do_sys_ioctl fs/ioctl.c:780 [inline]
__se_sys_ioctl fs/ioctl.c:778 [inline]
__x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:778
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45ca59
Code: Bad RIP value.
RSP: 002b:00007fc5b74b2c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004e98c0 RCX: 000000000045ca59
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000415 R14: 00000000004c6d6f R15: 00007fc5b74b36d4

Showing all locks held in the system:
1 lock held by khungtaskd/1147:
#0: ffffffff899bdd80 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5779
2 locks held by kworker/u5:0/1521:
#0: ffff888097167138 ((wq_completion)knbd1-recv){+.+.}-{0:0}, at: __write_once_size include/linux/compiler.h:279 [inline]
#0: ffff888097167138 ((wq_completion)knbd1-recv){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff888097167138 ((wq_completion)knbd1-recv){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:855 [inline]
#0: ffff888097167138 ((wq_completion)knbd1-recv){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:40 [inline]
#0: ffff888097167138 ((wq_completion)knbd1-recv){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:615 [inline]
#0: ffff888097167138 ((wq_completion)knbd1-recv){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline]
#0: ffff888097167138 ((wq_completion)knbd1-recv){+.+.}-{0:0}, at: process_one_work+0x844/0x16a0 kernel/workqueue.c:2239
#1: ffffc90005357dc0 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x878/0x16a0 kernel/workqueue.c:2243
1 lock held by in:imklog/6476:
2 locks held by agetty/6489:
#0: ffff88809ebb3098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267
#1: ffffc90000eb42e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x220/0x1b30 drivers/tty/n_tty.c:2156

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 1147 Comm: khungtaskd Not tainted 5.7.0-syzkaller #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+0x188/0x20d lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1e6/0x221 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline]
watchdog+0xa8c/0x1010 kernel/hung_task.c:289
kthread+0x388/0x470 kernel/kthread.c:268
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:351
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 3858 Comm: systemd-journal Not tainted 5.7.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:getname_flags fs/namei.c:150 [inline]
RIP: 0010:getname_flags+0x122/0x5b0 fs/namei.c:128
Code: 03 80 3c 02 00 0f 85 be 01 00 00 4c 89 f7 4d 89 34 24 ba e0 0f 00 00 48 89 de e8 e9 f1 ec 01 31 ff 49 89 c6 89 c6 89 44 24 04 <e8> a9 67 b2 ff 45 85 f6 0f 88 9e 01 00 00 e8 fb 65 b2 ff 44 89 f6
RSP: 0018:ffffc90001627df8 EFLAGS: 00000246
RAX: 000000000000001c RBX: 000055e1d31c89a3 RCX: ffffffff83ae5c52
RDX: 0000000000000000 RSI: 000000000000001c RDI: 0000000000000000
RBP: 0000000000000001 R08: ffff888094f5a480 R09: ffff8880aa1ec000
R10: 000000000000001c R11: fffff9400053f070 R12: ffff8880a7e0e940
R13: 0000000000000000 R14: 000000000000001c R15: ffffffff8a8b9b48
FS: 00007fb1526cd8c0(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb14fb8c000 CR3: 0000000094814000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
user_path_at_empty+0x2a/0x50 fs/namei.c:2632
user_path_at include/linux/namei.h:59 [inline]
do_faccessat+0x12c/0x830 fs/open.c:423
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x7fb1519899c7
Code: 83 c4 08 48 3d 01 f0 ff ff 73 01 c3 48 8b 0d c8 d4 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 b8 15 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a1 d4 2b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe422e0be8 EFLAGS: 00000246 ORIG_RAX: 0000000000000015
RAX: ffffffffffffffda RBX: 00007ffe422e3b00 RCX: 00007fb1519899c7
RDX: 00007fb1523faa00 RSI: 0000000000000000 RDI: 000055e1d31c89a3
RBP: 00007ffe422e0c20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000069 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ffe422e3b00 R15: 00007ffe422e1110

---
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