INFO: task hung in tty_poll
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syzbot
May 1, 2019, 3:35:06 AM5/1/19
to syzkaller-a...@googlegroups.com
Hello,
syzbot found the following crash on:
HEAD commit: 8fe42840 Merge 4.9.141 into android-4.9
git tree: android-4.9
console output: https://syzkaller.appspot.com/x/log.txt?x=135523cca00000
kernel config: https://syzkaller.appspot.com/x/.config?x=22a5ba9f73b6da1d
dashboard link: https://syzkaller.appspot.com/bug?extid=19d5127048d3d24a1aa9
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1020ac50a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=116f42b8a00000
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+19d512...@syzkaller.appspotmail.com
updating oom_score_adj for 7633 (syz-executor273) from 1000 to 1000 because
it shares mm with 7635 (syz-executor273). Report if this is unexpected.
updating oom_score_adj for 7637 (syz-executor273) from 1000 to 1000 because
it shares mm with 7640 (syz-executor273). Report if this is unexpected.
INFO: task syz-executor273:3839 blocked for more than 140 seconds.
Not tainted 4.9.141+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor273 D29544 3839 2490 0x00000000
ffff8801d7d6df00 0000000000000000 ffff8801d8003700 ffff8801da6b2f80
ffff8801db721018 ffff8801d7c87a00 ffffffff828075c2 ffff8801d7c87a10
ffffffff83cc2f20 ffff8801d99987ff 00000000000061b9 ffff8801db7218f0
Call Trace:
[<ffffffff82808aef>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
[<ffffffff828142d5>] schedule_timeout+0x735/0xe20 kernel/time/timer.c:1771
[<ffffffff81d4312c>] down_read_failed drivers/tty/tty_ldsem.c:241 [inline]
[<ffffffff81d4312c>] __ldsem_down_read_nested+0x33c/0x610
drivers/tty/tty_ldsem.c:332
[<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
[<ffffffff81d3ca85>] tty_ldisc_ref_wait+0x25/0x80
drivers/tty/tty_ldisc.c:275
[<ffffffff81d22005>] tty_poll+0xc5/0x190 drivers/tty/tty_io.c:2232
[<ffffffff815efcff>] ep_item_poll fs/eventpoll.c:811 [inline]
[<ffffffff815efcff>] ep_insert fs/eventpoll.c:1347 [inline]
[<ffffffff815efcff>] SYSC_epoll_ctl fs/eventpoll.c:1975 [inline]
[<ffffffff815efcff>] SyS_epoll_ctl+0x119f/0x25d0 fs/eventpoll.c:1861
[<ffffffff810056ef>] do_syscall_64+0x19f/0x550 arch/x86/entry/common.c:285
[<ffffffff82817893>] 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: [<ffffffff8131c0cc>]
check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
#0: (rcu_read_lock){......}, at: [<ffffffff8131c0cc>]
watchdog+0x11c/0xa20 kernel/hung_task.c:239
#1: (tasklist_lock){.+.+..}, at: [<ffffffff813fe63f>]
debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/2029:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/3838:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/3839:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4496:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/4497:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4500:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/4501:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4618:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/4620:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4638:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4639:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/4834:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4835:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/5502:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/5503:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/5506:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/5507:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/7438:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/7439:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/7653:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/7654:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/7655:
#0: (&tty->legacy_mutex){+.+.+.}, at: [<ffffffff81d4222a>]
tty_lock+0x6a/0xd0 drivers/tty/tty_mutex.c:18
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815992>]
ldsem_down_write+0x32/0x37 drivers/tty/tty_ldsem.c:393
=============================================
NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.141+ #1
ffff8801d9907d08 ffffffff81b42e79 0000000000000000 0000000000000000
0000000000000000 0000000000000001 ffffffff810983b0 ffff8801d9907d40
ffffffff81b4df89 0000000000000000 0000000000000000 0000000000000002
Call Trace:
[<ffffffff81b42e79>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81b42e79>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
[<ffffffff81b4df89>] nmi_cpu_backtrace.cold.0+0x48/0x87
lib/nmi_backtrace.c:99
[<ffffffff81b4df1c>] nmi_trigger_cpumask_backtrace+0x12c/0x151
lib/nmi_backtrace.c:60
[<ffffffff810984b4>] arch_trigger_cpumask_backtrace+0x14/0x20
arch/x86/kernel/apic/hw_nmi.c:37
[<ffffffff8131c65d>] trigger_all_cpu_backtrace include/linux/nmi.h:58
[inline]
[<ffffffff8131c65d>] check_hung_task kernel/hung_task.c:125 [inline]
[<ffffffff8131c65d>] check_hung_uninterruptible_tasks
kernel/hung_task.c:182 [inline]
[<ffffffff8131c65d>] watchdog+0x6ad/0xa20 kernel/hung_task.c:239
[<ffffffff81142c3d>] kthread+0x26d/0x300 kernel/kthread.c:211
[<ffffffff82817a5c>] 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 0xffffffff82816496
---
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 syzk...@googlegroups.com.
syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches
syzbot found the following crash on:
HEAD commit: 8fe42840 Merge 4.9.141 into android-4.9
git tree: android-4.9
console output: https://syzkaller.appspot.com/x/log.txt?x=135523cca00000
kernel config: https://syzkaller.appspot.com/x/.config?x=22a5ba9f73b6da1d
dashboard link: https://syzkaller.appspot.com/bug?extid=19d5127048d3d24a1aa9
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1020ac50a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=116f42b8a00000
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+19d512...@syzkaller.appspotmail.com
updating oom_score_adj for 7633 (syz-executor273) from 1000 to 1000 because
it shares mm with 7635 (syz-executor273). Report if this is unexpected.
updating oom_score_adj for 7637 (syz-executor273) from 1000 to 1000 because
it shares mm with 7640 (syz-executor273). Report if this is unexpected.
INFO: task syz-executor273:3839 blocked for more than 140 seconds.
Not tainted 4.9.141+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor273 D29544 3839 2490 0x00000000
ffff8801d7d6df00 0000000000000000 ffff8801d8003700 ffff8801da6b2f80
ffff8801db721018 ffff8801d7c87a00 ffffffff828075c2 ffff8801d7c87a10
ffffffff83cc2f20 ffff8801d99987ff 00000000000061b9 ffff8801db7218f0
Call Trace:
[<ffffffff82808aef>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
[<ffffffff828142d5>] schedule_timeout+0x735/0xe20 kernel/time/timer.c:1771
[<ffffffff81d4312c>] down_read_failed drivers/tty/tty_ldsem.c:241 [inline]
[<ffffffff81d4312c>] __ldsem_down_read_nested+0x33c/0x610
drivers/tty/tty_ldsem.c:332
[<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
[<ffffffff81d3ca85>] tty_ldisc_ref_wait+0x25/0x80
drivers/tty/tty_ldisc.c:275
[<ffffffff81d22005>] tty_poll+0xc5/0x190 drivers/tty/tty_io.c:2232
[<ffffffff815efcff>] ep_item_poll fs/eventpoll.c:811 [inline]
[<ffffffff815efcff>] ep_insert fs/eventpoll.c:1347 [inline]
[<ffffffff815efcff>] SYSC_epoll_ctl fs/eventpoll.c:1975 [inline]
[<ffffffff815efcff>] SyS_epoll_ctl+0x119f/0x25d0 fs/eventpoll.c:1861
[<ffffffff810056ef>] do_syscall_64+0x19f/0x550 arch/x86/entry/common.c:285
[<ffffffff82817893>] 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: [<ffffffff8131c0cc>]
check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
#0: (rcu_read_lock){......}, at: [<ffffffff8131c0cc>]
watchdog+0x11c/0xa20 kernel/hung_task.c:239
#1: (tasklist_lock){.+.+..}, at: [<ffffffff813fe63f>]
debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/2029:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/3838:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/3839:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4496:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/4497:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4500:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/4501:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4618:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/4620:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4638:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4639:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/4834:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/4835:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/5502:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/5503:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/5506:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/5507:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/7438:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/7439:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/7653:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor273/7654:
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>] SYSC_epoll_ctl
fs/eventpoll.c:1939 [inline]
#0: (&ep->mtx){+.+.+.}, at: [<ffffffff815ef3d9>]
SyS_epoll_ctl+0x879/0x25d0 fs/eventpoll.c:1861
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor273/7655:
#0: (&tty->legacy_mutex){+.+.+.}, at: [<ffffffff81d4222a>]
tty_lock+0x6a/0xd0 drivers/tty/tty_mutex.c:18
#1: (&tty->ldisc_sem){++++++}, at: [<ffffffff82815992>]
ldsem_down_write+0x32/0x37 drivers/tty/tty_ldsem.c:393
=============================================
NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.141+ #1
ffff8801d9907d08 ffffffff81b42e79 0000000000000000 0000000000000000
0000000000000000 0000000000000001 ffffffff810983b0 ffff8801d9907d40
ffffffff81b4df89 0000000000000000 0000000000000000 0000000000000002
Call Trace:
[<ffffffff81b42e79>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81b42e79>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
[<ffffffff81b4df89>] nmi_cpu_backtrace.cold.0+0x48/0x87
lib/nmi_backtrace.c:99
[<ffffffff81b4df1c>] nmi_trigger_cpumask_backtrace+0x12c/0x151
lib/nmi_backtrace.c:60
[<ffffffff810984b4>] arch_trigger_cpumask_backtrace+0x14/0x20
arch/x86/kernel/apic/hw_nmi.c:37
[<ffffffff8131c65d>] trigger_all_cpu_backtrace include/linux/nmi.h:58
[inline]
[<ffffffff8131c65d>] check_hung_task kernel/hung_task.c:125 [inline]
[<ffffffff8131c65d>] check_hung_uninterruptible_tasks
kernel/hung_task.c:182 [inline]
[<ffffffff8131c65d>] watchdog+0x6ad/0xa20 kernel/hung_task.c:239
[<ffffffff81142c3d>] kthread+0x26d/0x300 kernel/kthread.c:211
[<ffffffff82817a5c>] 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 0xffffffff82816496
---
This bug is generated by a bot. It may contain errors.
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