syzbot

refcount_t: increment on 0; use-after-free.
------------[ cut here ]------------
WARNING: CPU: 0 PID: 28200 at lib/refcount.c:152 refcount_inc+0x47/0x50 lib/refcount.c:152
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 28200 Comm: syz-executor7 Not tainted 4.13.0-rc7+ #60
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 panic+0x1e4/0x417 kernel/panic.c:180
 __warn+0x1c4/0x1d9 kernel/panic.c:541
 report_bug+0x211/0x2d0 lib/bug.c:183
 fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:190
 do_trap_no_signal arch/x86/kernel/traps.c:224 [inline]
 do_trap+0x260/0x390 arch/x86/kernel/traps.c:273
 do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:310
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:323
 invalid_op+0x1e/0x30 arch/x86/entry/entry_64.S:846
RIP: 0010:refcount_inc+0x47/0x50 lib/refcount.c:152
RSP: 0018:ffff8801cb557928 EFLAGS: 00010282
RAX: 000000000000002b RBX: ffffffff8608f514 RCX: 0000000000000000
RDX: 000000000000002b RSI: ffffffff8159319e RDI: ffffed00396aaf19
RBP: ffff8801cb557930 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff8608f3c0
R13: 0000000000000001 R14: ffff8801c27e3580 R15: dffffc0000000000
 attach_default_qdiscs net/sched/sch_generic.c:788 [inline]
 dev_activate+0x7d3/0xaa0 net/sched/sch_generic.c:829
 __dev_open+0x227/0x330 net/core/dev.c:1379
 __dev_change_flags+0x159/0x3d0 net/core/dev.c:6693
 dev_change_flags+0x88/0x140 net/core/dev.c:6758
 devinet_ioctl+0x123d/0x19a0 net/ipv4/devinet.c:1075
 inet_ioctl+0x117/0x1c0 net/ipv4/af_inet.c:900
 sock_do_ioctl+0x65/0xb0 net/socket.c:947
 sock_ioctl+0x2c2/0x440 net/socket.c:1044
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x451e59
RSP: 002b:00007f7999f6ac08 EFLAGS: 00000216 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000007180b0 RCX: 0000000000451e59
RDX: 000000002044ffe0 RSI: 0000000000008914 RDI: 0000000000000006
RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000216 R12: 00000000004b69f7
R13: 00007f7999f6ab48 R14: 00000000004b6a07 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..