syzbot

INFO: task syz-executor.2:28429 blocked for more than 140 seconds.
      Not tainted 4.9.189+ #20
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2  D28736 28429   2081 0x80000000
 0000000000000083 ffff8801c86917c0 ffff8801d4148000 ffff8801db621000
 ffff8801c733df00 ffff8801db621018 ffff8801d848fba0 ffffffff828176ae
 0000000041b58ab3 ffff8801c86917c0 00ff8801d848faf0 ffff8801db6218f0
Call Trace:
 [<00000000df82ac85>] schedule+0x92/0x1c0 kernel/sched/core.c:3546
 [<00000000e0fa49b9>] rwsem_down_read_failed+0x258/0x3e0 kernel/locking/rwsem-xadd.c:283
 [<000000009467b7a2>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<000000003932bb06>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<000000003932bb06>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<00000000e0c5ec88>] exit_mm kernel/exit.c:480 [inline]
 [<00000000e0c5ec88>] do_exit+0x3b7/0x2aa0 kernel/exit.c:828
 [<0000000053005bb0>] do_group_exit+0x111/0x300 kernel/exit.c:945
 [<0000000047e2aaa0>] SYSC_exit_group kernel/exit.c:956 [inline]
 [<0000000047e2aaa0>] SyS_exit_group+0x1d/0x20 kernel/exit.c:954
 [<000000003794ab50>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288
 [<00000000b41b43fc>] 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: [<0000000031cc86aa>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline]
 #0:  (rcu_read_lock){......}, at: [<0000000031cc86aa>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263
 #1:  (tasklist_lock){.+.+..}, at: [<0000000014ecd20f>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336
2 locks held by getty/2033:
 #0:  (&tty->ldisc_sem){++++++}, at: [<000000005bdacfdd>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<00000000ecd39b4b>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.2/28429:
 #0:  (&mm->mmap_sem){++++++}, at: [<00000000e0c5ec88>] exit_mm kernel/exit.c:480 [inline]
 #0:  (&mm->mmap_sem){++++++}, at: [<00000000e0c5ec88>] do_exit+0x3b7/0x2aa0 kernel/exit.c:828
1 lock held by syz-executor.2/28436:
 #0:  (&mm->mmap_sem){++++++}, at: [<00000000e0c5ec88>] exit_mm kernel/exit.c:480 [inline]
 #0:  (&mm->mmap_sem){++++++}, at: [<00000000e0c5ec88>] do_exit+0x3b7/0x2aa0 kernel/exit.c:828

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

NMI backtrace for cpu 1
CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.189+ #20
 ffff8801d98d7cc8 ffffffff81b64a91 0000000000000001 0000000000000000
 0000000000000001 ffffffff81099a01 dffffc0000000000 ffff8801d98d7d00
 ffffffff81b6fd2c 0000000000000001 0000000000000000 0000000000000001
Call Trace:
 [<000000005cd85f74>] __dump_stack lib/dump_stack.c:15 [inline]
 [<000000005cd85f74>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<000000007183f431>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<00000000051862b1>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<000000009836f9e5>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<000000004e384a25>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<000000004e384a25>] check_hung_task kernel/hung_task.c:126 [inline]
 [<000000004e384a25>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline]
 [<000000004e384a25>] watchdog+0x670/0xaf0 kernel/hung_task.c:263
 [<000000005b3e8634>] kthread+0x278/0x310 kernel/kthread.c:211
 [<000000008ffbdb5d>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 28446 Comm: syz-executor.2 Not tainted 4.9.189+ #20
task: 00000000adfb916d task.stack: 00000000e18836a8
RIP: 0010:[<ffffffff8120797e>] 
c [<0000000024a4219d>] lock_is_held+0x3e/0x140 kernel/locking/lockdep.c:3787
RSP: 0018:ffff8801d9e07a98  EFLAGS: 00000202
RAX: 0000000000000007 RBX: ffff8801ca0f17c0 RCX: 1ffffffff063fb70
RDX: 0000000000000000 RSI: 000000000000026c RDI: ffff8801ca0f206c
RBP: ffff8801d9e07ab0 R08: 0000000000000000 R09: ffff8801ca0f2090
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff830d5820
R13: 000000000000026c R14: 0000000000000000 R15: ffff8801ca0ecf60
FS:  00007fe9d848f700(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000014fad58 CR3: 00000001d5387000 CR4: 00000000001606b0
Stack:
 0000000000000000
c ffffffff82a51c00
c 000000000000026c
c ffff8801d9e07ae8
c
 ffffffff8116a3ea
c ffff8801ca0f17c0
c ffffffff82a51c00
c 000000000000026c
c
 0000000000000000
c ffff8801ca0ecf60
c ffff8801d9e07b28
c ffffffff8116a535
c
Call Trace:
 [<00000000df5676d0>] ___might_sleep+0x1ca/0x280 kernel/sched/core.c:7970
 [<000000004ea821df>] __might_sleep+0x95/0x1a0 kernel/sched/core.c:7961
 [<0000000060c967dd>] mutex_lock_nested+0x87/0x920 kernel/locking/mutex.c:620
 [<00000000db95eb55>] perf_mmap+0x4d9/0x1580 kernel/events/core.c:5278
 [<00000000ec01e64a>] mmap_region+0x7e7/0xfa0 mm/mmap.c:1726
 [<00000000206edc12>] do_mmap+0x539/0xbc0 mm/mmap.c:1505
 [<00000000f249f2dc>] do_mmap_pgoff include/linux/mm.h:2071 [inline]
 [<00000000f249f2dc>] vm_mmap_pgoff+0x179/0x1c0 mm/util.c:329
 [<00000000e75288cd>] SYSC_mmap_pgoff mm/mmap.c:1555 [inline]
 [<00000000e75288cd>] SyS_mmap_pgoff+0xfa/0x1b0 mm/mmap.c:1513
 [<000000008e3ff629>] SYSC_mmap arch/x86/kernel/sys_x86_64.c:96 [inline]
 [<000000008e3ff629>] SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:87
 [<000000003794ab50>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288
 [<00000000b41b43fc>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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