bisecting fixing commit since 3c8c23092588a23bf1856a64f58c37f477a413be
building syzkaller on ed7d41c582d6f194ff35353d8bfdf7681dc0718e
testing commit 3c8c23092588a23bf1856a64f58c37f477a413be with gcc (GCC) 8.4.1 20210217
kernel signature: 357e790c37ed29830c61c111a12e2b2bcfb396aa074becb8f9dcc61a862efb37
all runs: crashed: INFO: task hung in n_tty_poll
testing current HEAD fcfbdfe9626edd5bf00c732e093eed249ecdbfa1
testing commit fcfbdfe9626edd5bf00c732e093eed249ecdbfa1 with gcc (GCC) 8.4.1 20210217
kernel signature: 51254b9c10b17ee6cd98f32d5f718b0c37a00b6c47cc3153e5cb9bfaf2bd6a3e
all runs: crashed: INFO: task hung in n_tty_poll
revisions tested: 2, total time: 27m40.123639521s (build: 15m39.367287551s, test: 11m37.582506862s)
the crash still happens on HEAD
commit msg: Linux 4.19.197
crash: INFO: task hung in n_tty_poll
Bluetooth: hci3: command 0x0406 tx timeout
Bluetooth: hci2: command 0x0406 tx timeout
Bluetooth: hci4: command 0x0406 tx timeout
ieee802154 phy0 wpan0: encryption failed: -22
ieee802154 phy1 wpan1: encryption failed: -22
INFO: task syz-executor.2:9855 blocked for more than 140 seconds.
      Not tainted 4.19.197-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2  D27496  9855   8483 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2828 [inline]
 __schedule+0x80c/0x1f70 kernel/sched/core.c:3517
 schedule+0x7f/0x1b0 kernel/sched/core.c:3561
 schedule_timeout+0x6f6/0xd20 kernel/time/timer.c:1794
 do_wait_for_common kernel/sched/completion.c:83 [inline]
 __wait_for_common kernel/sched/completion.c:104 [inline]
 wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115
 wait_for_completion+0x18/0x20 kernel/sched/completion.c:136
 __flush_work+0x401/0x820 kernel/workqueue.c:2926
 flush_work+0xb/0x10 kernel/workqueue.c:2947
 tty_buffer_flush_work+0xd/0x10 drivers/tty/tty_buffer.c:613
 n_tty_poll+0x450/0x820 drivers/tty/n_tty.c:2410
 tty_poll+0x104/0x160 drivers/tty/tty_io.c:2110
 vfs_poll include/linux/poll.h:90 [inline]
 do_select+0x8de/0x1190 fs/select.c:507
 core_sys_select+0x414/0x6b0 fs/select.c:650
 do_pselect fs/select.c:731 [inline]
 __do_sys_pselect6 fs/select.c:772 [inline]
 __se_sys_pselect6+0x3a1/0x420 fs/select.c:757
 __x64_sys_pselect6+0xdc/0x1a0 fs/select.c:757
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4665d9
Code: 6e 6f 6e 65 75 b4 31 c0 e9 5e ff ff ff 0f 1f 40 00 48 83 f8 05 75 1f 48 8b 4c 24 30 81 39 63 72 61 73 75 96 80 79 04 68 75 90 <b8> 0b 00 00 00 66 90 e9 35 ff ff ff 48 83 f8 06 75 3d 48 8b 4c 24
RSP: 002b:00007f1d4be87188 EFLAGS: 00000246 ORIG_RAX: 000000000000010e
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000040
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020000140 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007ffeb809caef R14: 00007f1d4be87300 R15: 0000000000022000
INFO: task syz-executor.2:9976 blocked for more than 140 seconds.
      Not tainted 4.19.197-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2  D27944  9976   8483 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2828 [inline]
 __schedule+0x80c/0x1f70 kernel/sched/core.c:3517
 schedule+0x7f/0x1b0 kernel/sched/core.c:3561
 schedule_timeout+0x6f6/0xd20 kernel/time/timer.c:1794
 do_wait_for_common kernel/sched/completion.c:83 [inline]
 __wait_for_common kernel/sched/completion.c:104 [inline]
 wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115
 wait_for_completion+0x18/0x20 kernel/sched/completion.c:136
 __flush_work+0x401/0x820 kernel/workqueue.c:2926
 flush_work+0xb/0x10 kernel/workqueue.c:2947
 tty_buffer_flush_work+0xd/0x10 drivers/tty/tty_buffer.c:613
 n_tty_poll+0x450/0x820 drivers/tty/n_tty.c:2410
 tty_poll+0x104/0x160 drivers/tty/tty_io.c:2110
 vfs_poll include/linux/poll.h:90 [inline]
 do_select+0x8de/0x1190 fs/select.c:507
 core_sys_select+0x414/0x6b0 fs/select.c:650
 do_pselect fs/select.c:731 [inline]
 __do_sys_pselect6 fs/select.c:772 [inline]
 __se_sys_pselect6+0x3a1/0x420 fs/select.c:757
 __x64_sys_pselect6+0xdc/0x1a0 fs/select.c:757
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4665d9
Code: 6e 6f 6e 65 75 b4 31 c0 e9 5e ff ff ff 0f 1f 40 00 48 83 f8 05 75 1f 48 8b 4c 24 30 81 39 63 72 61 73 75 96 80 79 04 68 75 90 <b8> 0b 00 00 00 66 90 e9 35 ff ff ff 48 83 f8 06 75 3d 48 8b 4c 24
RSP: 002b:00007f1d4be45188 EFLAGS: 00000246 ORIG_RAX: 000000000000010e
RAX: ffffffffffffffda RBX: 000000000056c0b0 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000040
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020000140 R11: 0000000000000246 R12: 000000000056c0b0
R13: 00007ffeb809caef R14: 00007f1d4be45300 R15: 0000000000022000
INFO: task syz-executor.0:9890 blocked for more than 140 seconds.
      Not tainted 4.19.197-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0  D27800  9890   8492 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2828 [inline]
 __schedule+0x80c/0x1f70 kernel/sched/core.c:3517
 schedule+0x7f/0x1b0 kernel/sched/core.c:3561
 schedule_timeout+0x6f6/0xd20 kernel/time/timer.c:1794
 do_wait_for_common kernel/sched/completion.c:83 [inline]
 __wait_for_common kernel/sched/completion.c:104 [inline]
 wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115
 wait_for_completion+0x18/0x20 kernel/sched/completion.c:136
 __flush_work+0x401/0x820 kernel/workqueue.c:2926
 flush_work+0xb/0x10 kernel/workqueue.c:2947
 tty_buffer_flush_work+0xd/0x10 drivers/tty/tty_buffer.c:613
 n_tty_poll+0x450/0x820 drivers/tty/n_tty.c:2410
 tty_poll+0x104/0x160 drivers/tty/tty_io.c:2110
 vfs_poll include/linux/poll.h:90 [inline]
 do_select+0x8de/0x1190 fs/select.c:507
 core_sys_select+0x414/0x6b0 fs/select.c:650
 do_pselect fs/select.c:731 [inline]
 __do_sys_pselect6 fs/select.c:772 [inline]
 __se_sys_pselect6+0x3a1/0x420 fs/select.c:757
 __x64_sys_pselect6+0xdc/0x1a0 fs/select.c:757
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4665d9
Code: 6e 6f 6e 65 75 b4 31 c0 e9 5e ff ff ff 0f 1f 40 00 48 83 f8 05 75 1f 48 8b 4c 24 30 81 39 63 72 61 73 75 96 80 79 04 68 75 90 <b8> 0b 00 00 00 66 90 e9 35 ff ff ff 48 83 f8 06 75 3d 48 8b 4c 24
RSP: 002b:00007fce98db6188 EFLAGS: 00000246 ORIG_RAX: 000000000000010e
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000040
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020000140 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007ffe0e74795f R14: 00007fce98db6300 R15: 0000000000022000
INFO: task syz-executor.5:9939 blocked for more than 140 seconds.
      Not tainted 4.19.197-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D27656  9939   8488 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2828 [inline]
 __schedule+0x80c/0x1f70 kernel/sched/core.c:3517
 schedule+0x7f/0x1b0 kernel/sched/core.c:3561
 schedule_timeout+0x6f6/0xd20 kernel/time/timer.c:1794
 do_wait_for_common kernel/sched/completion.c:83 [inline]
 __wait_for_common kernel/sched/completion.c:104 [inline]
 wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115
 wait_for_completion+0x18/0x20 kernel/sched/completion.c:136
 __flush_work+0x401/0x820 kernel/workqueue.c:2926
 flush_work+0xb/0x10 kernel/workqueue.c:2947
 tty_buffer_flush_work+0xd/0x10 drivers/tty/tty_buffer.c:613
 n_tty_poll+0x450/0x820 drivers/tty/n_tty.c:2410
 tty_poll+0x104/0x160 drivers/tty/tty_io.c:2110
 vfs_poll include/linux/poll.h:90 [inline]
 do_select+0x8de/0x1190 fs/select.c:507
 core_sys_select+0x414/0x6b0 fs/select.c:650
 do_pselect fs/select.c:731 [inline]
 __do_sys_pselect6 fs/select.c:772 [inline]
 __se_sys_pselect6+0x3a1/0x420 fs/select.c:757
 __x64_sys_pselect6+0xdc/0x1a0 fs/select.c:757
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4665d9
Code: Bad RIP value.
RSP: 002b:00007f5a7dc9e188 EFLAGS: 00000246 ORIG_RAX: 000000000000010e
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000040
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020000140 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007ffc9664be7f R14: 00007f5a7dc9e300 R15: 0000000000022000
INFO: task syz-executor.1:9980 blocked for more than 140 seconds.
      Not tainted 4.19.197-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1  D27528  9980   8493 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2828 [inline]
 __schedule+0x80c/0x1f70 kernel/sched/core.c:3517
 schedule+0x7f/0x1b0 kernel/sched/core.c:3561
 schedule_timeout+0x6f6/0xd20 kernel/time/timer.c:1794
 do_wait_for_common kernel/sched/completion.c:83 [inline]
 __wait_for_common kernel/sched/completion.c:104 [inline]
 wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115
 wait_for_completion+0x18/0x20 kernel/sched/completion.c:136
 __flush_work+0x401/0x820 kernel/workqueue.c:2926
 flush_work+0xb/0x10 kernel/workqueue.c:2947
 tty_buffer_flush_work+0xd/0x10 drivers/tty/tty_buffer.c:613
 n_tty_poll+0x450/0x820 drivers/tty/n_tty.c:2410
 tty_poll+0x104/0x160 drivers/tty/tty_io.c:2110
 vfs_poll include/linux/poll.h:90 [inline]
 do_select+0x8de/0x1190 fs/select.c:507
 core_sys_select+0x414/0x6b0 fs/select.c:650
 do_pselect fs/select.c:731 [inline]
 __do_sys_pselect6 fs/select.c:772 [inline]
 __se_sys_pselect6+0x3a1/0x420 fs/select.c:757
 __x64_sys_pselect6+0xdc/0x1a0 fs/select.c:757
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4665d9
Code: Bad RIP value.
RSP: 002b:00007f0c3afa8188 EFLAGS: 00000246 ORIG_RAX: 000000000000010e
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000040
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020000140 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007ffc3d0bc54f R14: 00007f0c3afa8300 R15: 0000000000022000
INFO: task syz-executor.4:9986 blocked for more than 140 seconds.
      Not tainted 4.19.197-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4  D27496  9986   8486 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2828 [inline]
 __schedule+0x80c/0x1f70 kernel/sched/core.c:3517