WARNING: held lock freed in pppol2tp_release

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: ff33472c Linux 4.14.134
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17dda9d0600000
kernel config: https://syzkaller.appspot.com/x/.config?x=3559c2b3fb5dd4b2
dashboard link: https://syzkaller.appspot.com/bug?extid=a5d845a409d893a01c59
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a5d845...@syzkaller.appspotmail.com

=========================
WARNING: held lock freed!
4.14.134 #29 Not tainted
-------------------------
syz-executor.2/7221 is freeing memory ffff88805f816340-ffff88805f816b3f,
with a lock still held there!
(sk_lock-AF_PPPOX){+.+.}, at: [<ffffffff859c9f7e>] lock_sock
/./include/net/sock.h:1462 [inline]
(sk_lock-AF_PPPOX){+.+.}, at: [<ffffffff859c9f7e>]
pppol2tp_release+0x4e/0x300 /net/l2tp/l2tp_ppp.c:476
2 locks held by syz-executor.2/7221:
#0: (&sb->s_type->i_mutex_key#11){+.+.}, at: [<ffffffff84cbbe89>]
inode_lock /./include/linux/fs.h:718 [inline]
#0: (&sb->s_type->i_mutex_key#11){+.+.}, at: [<ffffffff84cbbe89>]
__sock_release+0x89/0x2b0 /net/socket.c:601
#1: (sk_lock-AF_PPPOX){+.+.}, at: [<ffffffff859c9f7e>] lock_sock
/./include/net/sock.h:1462 [inline]
#1: (sk_lock-AF_PPPOX){+.+.}, at: [<ffffffff859c9f7e>]
pppol2tp_release+0x4e/0x300 /net/l2tp/l2tp_ppp.c:476

stack backtrace:
CPU: 1 PID: 7221 Comm: syz-executor.2 Not tainted 4.14.134 #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack /lib/dump_stack.c:17 [inline]
dump_stack+0x138/0x19c /lib/dump_stack.c:53
print_freed_lock_bug /kernel/locking/lockdep.c:4456 [inline]
debug_check_no_locks_freed.cold+0x9d/0xa9 /kernel/locking/lockdep.c:4489
kfree+0xb1/0x270 /mm/slab.c:3812
sk_prot_free /net/core/sock.c:1504 [inline]
__sk_destruct+0x493/0x5d0 /net/core/sock.c:1583
sk_destruct+0x67/0x80 /net/core/sock.c:1591
__sk_free+0x54/0x230 /net/core/sock.c:1599
sk_free+0x35/0x40 /net/core/sock.c:1610
sock_put /./include/net/sock.h:1653 [inline]
pppol2tp_release+0x27d/0x300 /net/l2tp/l2tp_ppp.c:493
__sock_release+0xce/0x2b0 /net/socket.c:602
sock_close+0x1b/0x30 /net/socket.c:1139
__fput+0x275/0x7a0 /fs/file_table.c:210
____fput+0x16/0x20 /fs/file_table.c:244
task_work_run+0x114/0x190 /kernel/task_work.c:113
tracehook_notify_resume /./include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 /arch/x86/entry/common.c:164
prepare_exit_to_usermode /arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath /arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4bc/0x640 /arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x413501
RSP: 002b:00007fff92abb9a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000413501
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000005
RBP: 0000000000000000 R08: ffffffffffffffff R09: ffffffffffffffff
R10: 00007fff92abba80 R11: 0000000000000293 R12: 000000000075bfc8
R13: 000000000002755c R14: 0000000000760c10 R15: ffffffffffffffff
kobject: 'loop3' (ffff8880a4b04aa0): kobject_uevent_env
kobject: 'loop3' (ffff8880a4b04aa0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
==================================================================
BUG: KASAN: use-after-free in debug_spin_lock_before
/kernel/locking/spinlock_debug.c:83 [inline]
BUG: KASAN: use-after-free in do_raw_spin_lock+0x1eb/0x230
/kernel/locking/spinlock_debug.c:112
Read of size 4 at addr ffff88805f8163cc by task syz-executor.2/7221

CPU: 0 PID: 7221 Comm: syz-executor.2 Not tainted 4.14.134 #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack /lib/dump_stack.c:17 [inline]
dump_stack+0x138/0x19c /lib/dump_stack.c:53
print_address_description.cold+0x7c/0x1dc /mm/kasan/report.c:252
kasan_report_error /mm/kasan/report.c:351 [inline]
kasan_report /mm/kasan/report.c:409 [inline]
kasan_report.cold+0xa9/0x2af /mm/kasan/report.c:393
__asan_report_load4_noabort+0x14/0x20 /mm/kasan/report.c:429
debug_spin_lock_before /kernel/locking/spinlock_debug.c:83 [inline]
do_raw_spin_lock+0x1eb/0x230 /kernel/locking/spinlock_debug.c:112
__raw_spin_lock_bh /./include/linux/spinlock_api_smp.h:136 [inline]
_raw_spin_lock_bh+0x3b/0x50 /kernel/locking/spinlock.c:176
spin_lock_bh /./include/linux/spinlock.h:322 [inline]
release_sock+0x20/0x1b0 /net/core/sock.c:2772
pppol2tp_release+0x22b/0x300 /net/l2tp/l2tp_ppp.c:495
__sock_release+0xce/0x2b0 /net/socket.c:602
sock_close+0x1b/0x30 /net/socket.c:1139
__fput+0x275/0x7a0 /fs/file_table.c:210
____fput+0x16/0x20 /fs/file_table.c:244
task_work_run+0x114/0x190 /kernel/task_work.c:113
tracehook_notify_resume /./include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 /arch/x86/entry/common.c:164
prepare_exit_to_usermode /arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath /arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4bc/0x640 /arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x413501
RSP: 002b:00007fff92abb9a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000413501
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000005
RBP: 0000000000000000 R08: ffffffffffffffff R09: ffffffffffffffff
R10: 00007fff92abba80 R11: 0000000000000293 R12: 000000000075bfc8
R13: 000000000002755c R14: 0000000000760c10 R15: ffffffffffffffff

Allocated by task 7234:
save_stack_trace+0x16/0x20 /arch/x86/kernel/stacktrace.c:59
save_stack+0x45/0xd0 /mm/kasan/kasan.c:447
set_track /mm/kasan/kasan.c:459 [inline]
kasan_kmalloc /mm/kasan/kasan.c:551 [inline]
kasan_kmalloc+0xce/0xf0 /mm/kasan/kasan.c:529
__do_kmalloc /mm/slab.c:3720 [inline]
__kmalloc+0x15d/0x7a0 /mm/slab.c:3729
kmalloc /./include/linux/slab.h:493 [inline]
sk_prot_alloc+0x171/0x2a0 /net/core/sock.c:1467
sk_alloc+0x39/0xd70 /net/core/sock.c:1521
pppol2tp_create+0x32/0x1f0 /net/l2tp/l2tp_ppp.c:534
pppox_create+0xf7/0x210 /drivers/net/ppp/pppox.c:121
__sock_create+0x2f6/0x620 /net/socket.c:1275
sock_create /net/socket.c:1315 [inline]
SYSC_socket /net/socket.c:1345 [inline]
SyS_socket+0xd3/0x170 /net/socket.c:1325
do_syscall_64+0x1e8/0x640 /arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 7221:
save_stack_trace+0x16/0x20 /arch/x86/kernel/stacktrace.c:59
save_stack+0x45/0xd0 /mm/kasan/kasan.c:447
set_track /mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x75/0xc0 /mm/kasan/kasan.c:524
__cache_free /mm/slab.c:3496 [inline]
kfree+0xcc/0x270 /mm/slab.c:3815
sk_prot_free /net/core/sock.c:1504 [inline]
__sk_destruct+0x493/0x5d0 /net/core/sock.c:1583
sk_destruct+0x67/0x80 /net/core/sock.c:1591
__sk_free+0x54/0x230 /net/core/sock.c:1599
sk_free+0x35/0x40 /net/core/sock.c:1610
sock_put /./include/net/sock.h:1653 [inline]
pppol2tp_release+0x27d/0x300 /net/l2tp/l2tp_ppp.c:493
__sock_release+0xce/0x2b0 /net/socket.c:602
sock_close+0x1b/0x30 /net/socket.c:1139
__fput+0x275/0x7a0 /fs/file_table.c:210
____fput+0x16/0x20 /fs/file_table.c:244
task_work_run+0x114/0x190 /kernel/task_work.c:113
tracehook_notify_resume /./include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 /arch/x86/entry/common.c:164
prepare_exit_to_usermode /arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath /arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4bc/0x640 /arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff88805f816340
which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 140 bytes inside of
2048-byte region [ffff88805f816340, ffff88805f816b40)
The buggy address belongs to the page:
page:ffffea00017e0580 count:1 mapcount:0 mapping:ffff88805f816340 index:0x0
compound_mapcount: 0
flags: 0x1fffc0000008100(slab|head)
raw: 01fffc0000008100 ffff88805f816340 0000000000000000 0000000100000003
raw: ffffea0002953fa0 ffffea00017e4520 ffff8880aa800c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88805f816280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88805f816300: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
> ffff88805f816380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88805f816400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805f816480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.