syzbot

audit: type=1400 audit(1555710266.854:5): avc:  denied  { associate } for  pid=2249 comm="syz-executor.1" name="syz1" scontext=unconfined_u:object_r:unlabeled_t:s0 tcontext=system_u:object_r:unlabeled_t:s0 tclass=filesystem permissive=1
INFO: task syz-executor.0:2247 blocked for more than 140 seconds.
      Not tainted 4.9.169+ #43
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0  D25192  2247      1 0x00000004
 ffff8801c95897c0 0000000000000000 ffff8801db721000 ffff8801da6f2f80
 ffff8801db721018 ffff8801c9317988 ffffffff8280152e ffffffff828110ca
 0000000000000000 00ffffff842c0848 ffff8801db7218f0 1ffff10039262f20
Call Trace:
 [<00000000c5bea067>] schedule+0x92/0x1c0 kernel/sched/core.c:3546
 [<00000000bfae124a>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579
 [<00000000dbc7492d>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<00000000dbc7492d>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621
 [<000000008d107f62>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189
 [<00000000040a29b0>] loop_reread_partitions+0x7c/0x90 drivers/block/loop.c:638
 [<000000008092aec3>] loop_clr_fd+0x7dd/0xa60 drivers/block/loop.c:1082
 [<00000000c873fed1>] lo_ioctl+0x7b6/0x1a10 drivers/block/loop.c:1415
 [<00000000a0a36712>] __blkdev_driver_ioctl block/ioctl.c:294 [inline]
 [<00000000a0a36712>] blkdev_ioctl+0xe14/0x19e0 block/ioctl.c:590
 [<00000000af0ea2b4>] block_ioctl+0xde/0x120 fs/block_dev.c:1696
 [<00000000daace02b>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<00000000daace02b>] file_ioctl fs/ioctl.c:493 [inline]
 [<00000000daace02b>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677
 [<0000000091706496>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<0000000091706496>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<000000005c34837e>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 [<0000000076ba8cec>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<00000000e806f38e>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<00000000e806f38e>] watchdog+0x13c/0xae0 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<0000000066146396>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339
2 locks held by getty/2040:
 #0:  (&tty->ldisc_sem){++++++}, at: [<00000000da415ca2>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<000000001386221c>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
2 locks held by syz-executor.0/2247:
 #0:  (loop_ctl_mutex/1){+.+.+.}, at: [<000000003b04c693>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<000000008d107f62>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189
1 lock held by syz-executor.1/2249:
 #0:  (loop_ctl_mutex/1){+.+.+.}, at: [<000000003b04c693>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405
3 locks held by blkid/3319:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<0000000030c975d3>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587
 #1:  (loop_index_mutex){+.+.+.}, at: [<0000000082a73b83>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664
 #2:  (loop_ctl_mutex#2){+.+.+.}, at: [<00000000b80a519f>] __lo_release drivers/block/loop.c:1642 [inline]
 #2:  (loop_ctl_mutex#2){+.+.+.}, at: [<00000000b80a519f>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665
1 lock held by syz-executor.5/3320:
 #0:  (loop_ctl_mutex/1){+.+.+.}, at: [<000000003b04c693>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405
2 locks held by blkid/3321:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000fc3e6593>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000e5078914>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622
1 lock held by syz-executor.4/3322:
 #0:  (loop_ctl_mutex/1){+.+.+.}, at: [<000000003b04c693>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405
2 locks held by blkid/3323:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000fc3e6593>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000e5078914>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622
1 lock held by syz-executor.3/3324:
 #0:  (loop_ctl_mutex/1){+.+.+.}, at: [<000000003b04c693>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405
2 locks held by syz-executor.2/3325:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000fc3e6593>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000e5078914>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622
2 locks held by blkid/3326:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000fc3e6593>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000e5078914>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622
1 lock held by blkid/3327:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000fc3e6593>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273

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

NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.169+ #43
 ffff8801d98d7cc8 ffffffff81b4f7f1 0000000000000000 0000000000000000
 0000000000000000 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00
 ffffffff81b5aa8c 0000000000000000 0000000000000000 0000000000000000
Call Trace:
 [<00000000e26243c1>] __dump_stack lib/dump_stack.c:15 [inline]
 [<00000000e26243c1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<000000005f8adca3>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<00000000c77b010e>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<000000001bcc9b0e>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<000000004bc002e2>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<000000004bc002e2>] check_hung_task kernel/hung_task.c:125 [inline]
 [<000000004bc002e2>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<000000004bc002e2>] watchdog+0x661/0xae0 kernel/hung_task.c:239
 [<0000000071fea858>] kthread+0x278/0x310 kernel/kthread.c:211
 [<00000000d1fd0387>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff828105a2