Message-ID: <000000000000e02bf505866414ae@google.com>
Date:   Sat, 13 Apr 2019 00:08:08 -0700
From:   syzbot <syzbot+9880e421ec82313d6527@...kaller.appspotmail.com>
To:     ap420073@...il.com, avagin@...il.com, dbueso@...e.de,
        ebiederm@...ssion.com, linux-kernel@...r.kernel.org,
        oleg@...hat.com, prsood@...eaurora.org,
        syzkaller-bugs@...glegroups.com, tj@...nel.org
Subject: INFO: task hung in do_exit

Hello,

syzbot found the following crash on:

HEAD commit:    8ee15f32 Merge tag 'dma-mapping-5.1-1' of git://git.infrad..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15a512d3200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4fb64439e07a1ec0
dashboard link: https://syzkaller.appspot.com/bug?extid=9880e421ec82313d6527
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=149b89af200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9880e421ec82313d6527@...kaller.appspotmail.com

INFO: task syz-executor.4:13600 blocked for more than 143 seconds.
       Not tainted 5.1.0-rc4+ #65
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4  D28384 13600   8046 0x80000000
Call Trace:
  context_switch kernel/sched/core.c:2877 [inline]
  __schedule+0x817/0x1cc0 kernel/sched/core.c:3518
  schedule+0x92/0x180 kernel/sched/core.c:3562
  __rwsem_down_read_failed_common kernel/locking/rwsem-xadd.c:285 [inline]
  rwsem_down_read_failed+0x213/0x420 kernel/locking/rwsem-xadd.c:302
  call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
  __down_read arch/x86/include/asm/rwsem.h:83 [inline]
  down_read+0x49/0x90 kernel/locking/rwsem.c:26
  exit_mm kernel/exit.c:512 [inline]
  do_exit+0x443/0x2fa0 kernel/exit.c:863
  do_group_exit+0x135/0x370 kernel/exit.c:980
  __do_sys_exit_group kernel/exit.c:991 [inline]
  __se_sys_exit_group kernel/exit.c:989 [inline]
  __x64_sys_exit_group+0x44/0x50 kernel/exit.c:989
  do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458c29
Code: Bad RIP value.
RSP: 002b:00007ffffcf8a138 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 000000000000001e RCX: 0000000000458c29
RDX: 00000000004129e1 RSI: fffffffffffffff7 RDI: 0000000000000000
RBP: 0000000000000000 R08: 000000000009a64e R09: 00007ffffcf8a190
R10: 000000000009a64e R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffffcf8a190 R14: 0000000000000000 R15: 00007ffffcf8a1a0
INFO: task syz-executor.4:13603 blocked for more than 143 seconds.
       Not tainted 5.1.0-rc4+ #65
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4  D28200 13603   8046 0x80000000
Call Trace:
  context_switch kernel/sched/core.c:2877 [inline]
  __schedule+0x817/0x1cc0 kernel/sched/core.c:3518
  schedule+0x92/0x180 kernel/sched/core.c:3562
  __rwsem_down_read_failed_common kernel/locking/rwsem-xadd.c:285 [inline]
  rwsem_down_read_failed+0x213/0x420 kernel/locking/rwsem-xadd.c:302
  call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
  __down_read arch/x86/include/asm/rwsem.h:83 [inline]
  down_read+0x49/0x90 kernel/locking/rwsem.c:26
  exit_mm kernel/exit.c:512 [inline]
  do_exit+0x443/0x2fa0 kernel/exit.c:863
  do_group_exit+0x135/0x370 kernel/exit.c:980
  get_signal+0x399/0x1d50 kernel/signal.c:2577
  do_signal+0x87/0x1940 arch/x86/kernel/signal.c:816
  exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:162
  prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
  do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458c29
Code: Bad RIP value.
RSP: 002b:00007f55040dbcf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000073bf08 RCX: 0000000000458c29
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000073bf08
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000073bf0c
R13: 00007ffffcf89f3f R14: 00007f55040dc9c0 R15: 000000000073bf0c

Showing all locks held in the system:
1 lock held by khungtaskd/1042:
  #0: 00000000e7920387 (rcu_read_lock){....}, at:  
debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:5061
1 lock held by rsyslogd/7885:
  #0: 00000000746102cf (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110  
fs/file.c:801
2 locks held by getty/7997:
  #0: 0000000084730aa3 (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
  #1: 0000000095194d1b (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/7998:
  #0: 00000000f2a2e523 (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
  #1: 00000000c8e15d18 (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/7999:
  #0: 0000000070592706 (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
  #1: 00000000a567a5f4 (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/8000:
  #0: 0000000088e68b88 (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
  #1: 00000000150e7fab (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/8001:
  #0: 000000001f261fc9 (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
  #1: 0000000090482210 (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/8002:
  #0: 00000000003fc912 (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
  #1: 00000000a81ef369 (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/8003:
  #0: 00000000620d61b3 (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
  #1: 000000002d752e92 (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.4/13600:
  #0: 0000000016ce688c (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512  
[inline]
  #0: 0000000016ce688c (&mm->mmap_sem){++++}, at: do_exit+0x443/0x2fa0  
kernel/exit.c:863
1 lock held by syz-executor.4/13603:
  #0: 0000000016ce688c (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512  
[inline]
  #0: 0000000016ce688c (&mm->mmap_sem){++++}, at: do_exit+0x443/0x2fa0  
kernel/exit.c:863
1 lock held by syz-executor.4/13611:

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

NMI backtrace for cpu 1
CPU: 1 PID: 1042 Comm: khungtaskd Not tainted 5.1.0-rc4+ #65
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+0x63/0xa4 lib/nmi_backtrace.c:101
  nmi_trigger_cpumask_backtrace+0x1be/0x236 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:204 [inline]
  watchdog+0x9b7/0xec0 kernel/hung_task.c:288
  kthread+0x357/0x430 kernel/kthread.c:253
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 1 to CPUs 0:


---
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