Created attachment 727789 [details]
syzkaller reproducer

pps pps0: new PPS source pty_master1
pps_ldisc: cannot open tty ldisc "/dev/ptm1"
Kernel panic - not syncing: Couldn't open N_TTY ldisc for ptm1 --- error -12.
CPU: 2 PID: 3623 Comm: syz-executor2 Not tainted
4.12.0-rc4-0.g723b913-syzkaller #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.0.0-prebuilt.qemu-project.org 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x115/0x1de lib/dump_stack.c:52
 panic+0x1df/0x48b kernel/panic.c:180
 tty_set_ldisc+0x75d/0xa00 drivers/tty/tty_ldisc.c:523
 tty_ioctl+0x86c/0x18f0 drivers/tty/tty_io.c:2166
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1cf/0x17f0 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x94/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x23/0xc2
RIP: 0033:0x7f53b8c11b89
RSP: 002b:00007f53b9158c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000056188bbaa0a8 RCX: 00007f53b8c11b89
RDX: 0000000020a54ffc RSI: 0000000000005423 RDI: 0000000000000006
RBP: 0000000000000046 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fffa146122e
R13: 00007fffa146122f R14: 00007f53b9159700 R15: 0000000000000000
Kernel Offset: 0x15000000 from 0xffffffff81000000 (relocation range:
0xffffffff80000000-0xffffffffbfffffff)
Rebooting in 90 seconds..