WARNING: kobject bug in copy_user_generic_unrolled

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
1bad9ce155a7c010a9a5f3261ad12a6a8eccfb2c (Fri Apr 13 19:27:11 2018 +0000)
Merge tag 'sh-for-4.17' of git://git.libc.org/linux-sh
syzbot dashboard link:
https://syzkaller.appspot.com/bug?extid=34621cb6ebf1b19e3052

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output:
https://syzkaller.appspot.com/x/log.txt?id=5733611076583424
Kernel config:
https://syzkaller.appspot.com/x/.config?id=-5947642240294114534
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org
vi...@zeniv.linux.org.uk]

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+34621c...@syzkaller.appspotmail.com
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details.
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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+0x1b9/0x294 lib/dump_stack.c:113
kobject_add_internal failed for ppp0 (error: -12 parent: net)
handle_userfault.cold.32+0x44/0x57 fs/userfaultfd.c:430
WARNING: CPU: 0 PID: 11451 at lib/kobject.c:242
kobject_add_internal+0x42c/0xba0 lib/kobject.c:240
Kernel panic - not syncing: panic_on_warn set ...

do_anonymous_page mm/memory.c:3147 [inline]
handle_pte_fault mm/memory.c:3961 [inline]
__handle_mm_fault+0x34be/0x4150 mm/memory.c:4087
handle_mm_fault+0x53a/0xc70 mm/memory.c:4124
__do_page_fault+0x60b/0xe40 arch/x86/mm/fault.c:1399
do_page_fault+0xee/0x8a7 arch/x86/mm/fault.c:1474
page_fault+0x25/0x50 arch/x86/entry/entry_64.S:1159
RIP: 0010:copy_user_generic_unrolled+0x86/0xc0
arch/x86/lib/copy_user_64.S:65
RSP: 0018:ffff8801891f7b98 EFLAGS: 00010202
RAX: ffffed003123ef83 RBX: 0000000000000010 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 0000000020013000 RDI: ffff8801891f7c08
RBP: ffff8801891f7bd0 R08: ffffed003123ef83 R09: ffffed003123ef81
R10: ffffed003123ef82 R11: ffff8801891f7c17 R12: 0000000020013010
R13: 0000000020013000 R14: ffff8801891f7c08 R15: 00007ffffffff000
copy_from_user include/linux/uaccess.h:147 [inline]
get_timespec64+0x75/0x180 kernel/time/time.c:861
do_pselect fs/select.c:717 [inline]
SYSC_pselect6 fs/select.c:777 [inline]
SyS_pselect6+0x1ca/0x680 fs/select.c:762
do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x455319
RSP: 002b:00007f82b1f1cc68 EFLAGS: 00000246 ORIG_RAX: 000000000000010e
RAX: ffffffffffffffda RBX: 00007f82b1f1d6d4 RCX: 0000000000455319
RDX: 0000000020011000 RSI: 0000000020011fc0 RDI: 0000000000000040
RBP: 000000000072bea0 R08: 0000000020013000 R09: 0000000020001ff8
R10: 0000000020003000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000473 R14: 00000000006f9b68 R15: 0000000000000000
CPU: 0 PID: 11451 Comm: syz-executor2 Not tainted 4.16.0+ #1
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+0x1b9/0x294 lib/dump_stack.c:113
panic+0x22f/0x4de kernel/panic.c:184
__warn.cold.8+0x163/0x1b3 kernel/panic.c:536
report_bug+0x252/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x1de/0x490 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:991
RIP: 0010:kobject_add_internal+0x42c/0xba0 lib/kobject.c:240
RSP: 0018:ffff880189f37220 EFLAGS: 00010286
RAX: 000000000000003d RBX: ffff8801aaa5eae8 RCX: ffffc90003ec0000
RDX: 0000000000040000 RSI: ffffffff815fa581 RDI: ffff880189f36d80
RBP: ffff880189f37318 R08: ffff8801aa67e6c0 R09: 0000000000000006
R10: ffff8801aa67e6c0 R11: 0000000000000000 R12: 00000000fffffff4
R13: ffff8801d6a2ce80 R14: ffffffff882a9fe0 R15: ffff8801d9fc8f00
kobject_add_varg lib/kobject.c:364 [inline]
kobject_add+0x13a/0x190 lib/kobject.c:408
device_add+0x3a5/0x16d0 drivers/base/core.c:1796
netdev_register_kobject+0x180/0x380 net/core/net-sysfs.c:1604
register_netdevice+0x997/0x11c0 net/core/dev.c:7961
ppp_unit_register drivers/net/ppp/ppp_generic.c:1010 [inline]
ppp_dev_configure+0xa8b/0xe70 drivers/net/ppp/ppp_generic.c:1066
ppp_create_interface drivers/net/ppp/ppp_generic.c:3030 [inline]
ppp_unattached_ioctl drivers/net/ppp/ppp_generic.c:865 [inline]
ppp_ioctl+0x1d0d/0x30b2 drivers/net/ppp/ppp_generic.c:601
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
SYSC_ioctl fs/ioctl.c:708 [inline]
SyS_ioctl+0x24/0x30 fs/ioctl.c:706
do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x455319
RSP: 002b:00007f2a14aa7c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f2a14aa86d4 RCX: 0000000000455319
RDX: 0000000020000a80 RSI: 00000000c004743e RDI: 0000000000000014
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000015
R13: 00000000000001e4 R14: 00000000006f5e00 R15: 0000000000000006
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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[Dmitry Vyukov]

Several intermixed reports and as result incorrect guilty frame.
#syz invalid

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