WARNING in __kthread_bind_mask

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    bcb67f0f Add linux-next specific files for 20190412
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=165912d3200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=35c479ecf64ba753
dashboard link: https://syzkaller.appspot.com/bug?extid=6d4a92619eb0ad08602b
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14c9ebbb200000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=153f76dd200000

The bug was bisected to:

commit 6c271ce2f1d572f7fa225700a13cfe7ced492434
Author: Jens Axboe <axboe@xxxxxxxxx>
Date:   Thu Jan 10 18:22:30 2019 +0000

    io_uring: add submission polling

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=143498f3200000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=163498f3200000
console output: https://syzkaller.appspot.com/x/log.txt?x=123498f3200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6d4a92619eb0ad08602b@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 6c271ce2f1d5 ("io_uring: add submission polling")

WARNING: CPU: 0 PID: 7822 at kernel/kthread.c:399  
__kthread_bind_mask+0x3b/0xc0 kernel/kthread.c:399
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 7822 Comm: syz-executor030 Not tainted 5.1.0-rc4-next-20190412  
#24
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
 panic+0x2cb/0x72b kernel/panic.c:214
 __warn.cold+0x20/0x46 kernel/panic.c:576
 report_bug+0x263/0x2b0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:179 [inline]
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:__kthread_bind_mask+0x3b/0xc0 kernel/kthread.c:399
Code: 48 89 fb e8 f7 ab 24 00 4c 89 e6 48 89 df e8 ac e1 02 00 31 ff 49 89  
c4 48 89 c6 e8 7f ad 24 00 4d 85 e4 75 15 e8 d5 ab 24 00 <0f> 0b e8 ce ab  
24 00 5b 41 5c 41 5d 41 5e 5d c3 e8 c0 ab 24 00 4c
RSP: 0018:ffff8880a89bfbb8 EFLAGS: 00010293
RAX: ffff88808ca7a280 RBX: ffff8880a98e4380 RCX: ffffffff814bdd11
RDX: 0000000000000000 RSI: ffffffff814bdd1b RDI: 0000000000000007
RBP: ffff8880a89bfbd8 R08: ffff88808ca7a280 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff87691148 R14: ffff8880a98e43a0 R15: ffffffff81c91e10
 __kthread_bind kernel/kthread.c:412 [inline]
 kthread_unpark+0x123/0x160 kernel/kthread.c:480
 kthread_stop+0xfa/0x6c0 kernel/kthread.c:556
 io_sq_thread_stop fs/io_uring.c:2057 [inline]
 io_sq_thread_stop fs/io_uring.c:2052 [inline]
 io_finish_async+0xab/0x180 fs/io_uring.c:2064
 io_ring_ctx_free fs/io_uring.c:2534 [inline]
 io_ring_ctx_wait_and_kill+0x133/0x510 fs/io_uring.c:2591
 io_uring_release+0x42/0x50 fs/io_uring.c:2599
 __fput+0x2e5/0x8d0 fs/file_table.c:278
 ____fput+0x16/0x20 fs/file_table.c:309
 task_work_run+0x14a/0x1c0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x90a/0x2fa0 kernel/exit.c:876
 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: 0033:0x43ee98
Code: Bad RIP value.
RSP: 002b:00007fff28656a18 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043ee98
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004be6a8 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d0180 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


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