KASAN: use-after-free Read in lock_sock_nested

Hello,

syzbot found the following crash on:

HEAD commit: 68d7a45e Linux 4.14.113
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17817b28a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=dbf1fde4d7489e1c
dashboard link: https://syzkaller.appspot.com/bug?extid=6a7aff016d74d4c124eb
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=131d195ca00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email protected]

IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready
8021q: adding VLAN 0 to HW filter on device batadv0
IPv6: ADDRCONF(NETDEV_CHANGE): bond0: link becomes ready
==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x303c/0x45e0
kernel/locking/lockdep.c:3365
Read of size 8 at addr ffff8880a9bca6e0 by task syz-executor.0/7387

CPU: 0 PID: 7387 Comm: syz-executor.0 Not tainted 4.14.113 #3
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+0xaf/0x2b5 mm/kasan/report.c:393
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
__lock_acquire+0x303c/0x45e0 kernel/locking/lockdep.c:3365
lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x33/0x50 kernel/locking/spinlock.c:176
spin_lock_bh include/linux/spinlock.h:322 [inline]
lock_sock_nested+0x3f/0x110 net/core/sock.c:2760
lock_sock include/net/sock.h:1462 [inline]
pppol2tp_release+0x4e/0x300 net/l2tp/l2tp_ppp.c:476
__sock_release+0xd3/0x2c0 net/socket.c:602
sock_close+0x1b/0x30 net/socket.c:1139
__fput+0x277/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x119/0x190 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:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:267 [inline]
do_syscall_64+0x4a9/0x630 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4129e1
RSP: 002b:00007fffaae57300 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 00000000004129e1
RDX: 0000000000000000 RSI: 0000000000000081 RDI: 0000000000000005
RBP: 0000000000740490 R08: 0000000000740488 R09: 00000000000c5949
R10: 00007fffaae573c0 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000003 R15: 000000000073bf0c

Allocated by task 7390:
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:1470
sk_alloc+0x39/0xd70 net/core/sock.c:1524
pppol2tp_create+0x32/0x1f0 net/l2tp/l2tp_ppp.c:534
pppox_create+0xfc/0x210 drivers/net/ppp/pppox.c:121
__sock_create+0x2fb/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+0x1eb/0x630 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 7387:
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:1507 [inline]
__sk_destruct+0x495/0x5d0 net/core/sock.c:1586
sk_destruct+0x67/0x80 net/core/sock.c:1594
__sk_free+0x54/0x230 net/core/sock.c:1602
sk_free+0x35/0x40 net/core/sock.c:1613
sock_put include/net/sock.h:1653 [inline]
pppol2tp_session_sock_put+0x66/0x80 net/l2tp/l2tp_ppp.c:271
l2tp_tunnel_closeall+0x288/0x390 net/l2tp/l2tp_core.c:1343
l2tp_udp_encap_destroy+0x99/0x100 net/l2tp/l2tp_core.c:1366
udpv6_destroy_sock+0xb6/0xd0 net/ipv6/udp.c:1444
sk_common_release+0x6d/0x320 net/core/sock.c:2987
udp_lib_close+0x16/0x20 include/net/udp.h:203
inet_release+0xf2/0x1c0 net/ipv4/af_inet.c:425
inet6_release+0x53/0x80 net/ipv6/af_inet6.c:450
__sock_release+0xd3/0x2c0 net/socket.c:602
sock_close+0x1b/0x30 net/socket.c:1139
__fput+0x277/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x119/0x190 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:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:267 [inline]
do_syscall_64+0x4a9/0x630 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8880a9bca640
which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 160 bytes inside of
2048-byte region [ffff8880a9bca640, ffff8880a9bcae40)
The buggy address belongs to the page:
page:ffffea0002a6f280 count:1 mapcount:0 mapping:ffff8880a9bca640 index:0x0
compound_mapcount: 0
flags: 0x1fffc0000008100(slab|head)
raw: 01fffc0000008100 ffff8880a9bca640 0000000000000000 0000000100000003
raw: ffffea0002a4f120 ffffea00022a6fa0 ffff8880aa800c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a9bca580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a9bca600: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
> ffff8880a9bca680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880a9bca700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a9bca780: 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 [email protected].

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syzbot has found a reproducer for the following issue on:

HEAD commit: 7f2c5eb4 Linux 4.14.191
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=136a31ea900000
kernel config: https://syzkaller.appspot.com/x/.config?x=881f1aee9620bf9f
dashboard link: https://syzkaller.appspot.com/bug?extid=6a7aff016d74d4c124eb
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16472d70900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1451da42900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x2c57/0x3f20 kernel/locking/lockdep.c:3369
Read of size 8 at addr ffff88808e0f66e0 by task kworker/1:1/6551

CPU: 1 PID: 6551 Comm: kworker/1:1 Not tainted 4.14.191-syzkaller #0
Workqueue: events l2cap_chan_timeout
dump_stack+0x1b2/0x283 lib/dump_stack.c:58
print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
kasan_report_error.cold+0x8a/0x194 mm/kasan/report.c:351
kasan_report mm/kasan/report.c:409 [inline]
__asan_report_load8_noabort+0x68/0x70 mm/kasan/report.c:430
__lock_acquire+0x2c57/0x3f20 kernel/locking/lockdep.c:3369
lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:176
spin_lock_bh include/linux/spinlock.h:322 [inline]
lock_sock_nested+0x39/0x100 net/core/sock.c:2767
l2cap_sock_teardown_cb+0x7b/0x400 net/bluetooth/l2cap_sock.c:1329
l2cap_chan_close+0x24b/0x770 net/bluetooth/l2cap_core.c:758
l2cap_chan_timeout+0x134/0x1e0 net/bluetooth/l2cap_core.c:427
process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
kthread+0x30d/0x420 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 7359:
save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
__do_kmalloc mm/slab.c:3720 [inline]
__kmalloc+0x15a/0x400 mm/slab.c:3729
kmalloc include/linux/slab.h:493 [inline]
sk_prot_alloc+0x1ba/0x290 net/core/sock.c:1467
sk_alloc+0x36/0xcd0 net/core/sock.c:1521
l2cap_sock_alloc.constprop.0+0x31/0x210 net/bluetooth/l2cap_sock.c:1591
l2cap_sock_create+0xdd/0x170 net/bluetooth/l2cap_sock.c:1637
bt_sock_create+0x13b/0x280 net/bluetooth/af_bluetooth.c:130
__sock_create+0x303/0x620 net/socket.c:1275
SyS_socket+0xd1/0x1b0 net/socket.c:1325
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 7363:
save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kfree+0xc9/0x250 mm/slab.c:3815
sk_prot_free net/core/sock.c:1504 [inline]
__sk_destruct+0x577/0x6e0 net/core/sock.c:1582
sk_destruct net/core/sock.c:1597 [inline]
__sk_free+0xd9/0x2d0 net/core/sock.c:1605
sk_free+0x2b/0x40 net/core/sock.c:1616
sock_put include/net/sock.h:1658 [inline]
l2cap_sock_kill.part.0+0x5b/0x70 net/bluetooth/l2cap_sock.c:1056
l2cap_sock_kill net/bluetooth/l2cap_sock.c:1207 [inline]
l2cap_sock_release+0x146/0x180 net/bluetooth/l2cap_sock.c:1205
__sock_release+0xcd/0x2b0 net/socket.c:602
sock_close+0x15/0x20 net/socket.c:1139
__fput+0x25f/0x7a0 fs/file_table.c:210
task_work_run+0x11f/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1ad/0x200 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+0x4a3/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x46/0xbb

The buggy address belongs to the object at ffff88808e0f6640
2048-byte region [ffff88808e0f6640, ffff88808e0f6e40)
page:ffffea0002383d80 count:1 mapcount:0 mapping:ffff88808e0f6640 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff88808e0f6640 0000000000000000 0000000100000003
raw: ffffea00023b4a20 ffffea0002458d20 ffff88812fe52c40 0000000000000000
ffff88808e0f6580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88808e0f6600: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff88808e0f6680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88808e0f6700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88808e0f6780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================