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l2tp_core: tunl 4: fd 7 wrong protocol, got 1, expected 17
l2tp_core: tunl 4: fd 4 wrong protocol, got 1, expected 17
l2tp_core: tunl 4: fd 7 wrong protocol, got 1, expected 17
l2tp_core: tunl 4: fd 4 wrong protocol, got 1, expected 17
==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x2eff/0x3640 kernel/locking/lockdep.c:3224
Read of size 8 at addr ffff8801d3f99a20 by task syzkaller540979/4836

CPU: 0 PID: 4836 Comm: syzkaller540979 Not tainted 4.9.83-ga92bb8d #51
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d387f600 ffffffff81d95149 ffffea00074fe600 ffff8801d3f99a20
 0000000000000000 ffff8801d3f99a20 ffff8801d3f99a20 ffff8801d387f638
 ffffffff8153e213 ffff8801d3f99a20 0000000000000008 0000000000000000
Call Trace:
 [<ffffffff81d95149>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d95149>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8153e213>] print_address_description+0x73/0x280 mm/kasan/report.c:252
 [<ffffffff8153e735>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8153e735>] kasan_report+0x275/0x360 mm/kasan/report.c:408
 [<ffffffff8153e894>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff8123ef2f>] __lock_acquire+0x2eff/0x3640 kernel/locking/lockdep.c:3224
 [<ffffffff812400ae>] lock_acquire+0x12e/0x410 kernel/locking/lockdep.c:3756
 [<ffffffff838b43da>] __raw_spin_lock_bh include/linux/spinlock_api_smp.h:137 [inline]
 [<ffffffff838b43da>] _raw_spin_lock_bh+0x3a/0x50 kernel/locking/spinlock.c:175
 [<ffffffff82ee5013>] spin_lock_bh include/linux/spinlock.h:307 [inline]
 [<ffffffff82ee5013>] lock_sock_nested+0x43/0x120 net/core/sock.c:2503
 [<ffffffff8358f400>] lock_sock include/net/sock.h:1404 [inline]
 [<ffffffff8358f400>] pppol2tp_release+0x50/0x2e0 net/l2tp/l2tp_ppp.c:476
 [<ffffffff82ed589d>] sock_release+0x8d/0x1e0 net/socket.c:599
 [<ffffffff82ed5a06>] sock_close+0x16/0x20 net/socket.c:1046
 [<ffffffff8157580c>] __fput+0x28c/0x6e0 fs/file_table.c:208
 [<ffffffff81575ce5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff81195855>] task_work_run+0x115/0x190 kernel/task_work.c:116
 [<ffffffff8113c2c7>] exit_task_work include/linux/task_work.h:21 [inline]
 [<ffffffff8113c2c7>] do_exit+0x7e7/0x2a40 kernel/exit.c:833
 [<ffffffff811429d8>] do_group_exit+0x108/0x320 kernel/exit.c:937
 [<ffffffff81165854>] get_signal+0x4d4/0x14e0 kernel/signal.c:2317
 [<ffffffff81052c87>] do_signal+0x87/0x19f0 arch/x86/kernel/signal.c:807
 [<ffffffff81003a31>] exit_to_usermode_loop+0xe1/0x120 arch/x86/entry/common.c:157
 [<ffffffff81007261>] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 [<ffffffff81007261>] syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 [<ffffffff81007261>] do_syscall_32_irqs_on arch/x86/entry/common.c:331 [inline]
 [<ffffffff81007261>] do_fast_syscall_32+0x5c1/0x870 arch/x86/entry/common.c:387
 [<ffffffff838b6590>] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137

Allocated by task 4837:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:609
 __kmalloc+0x11d/0x310 mm/slub.c:3741
 kmalloc include/linux/slab.h:495 [inline]
 sk_prot_alloc+0x101/0x2a0 net/core/sock.c:1338
 sk_alloc+0x3a/0x3a0 net/core/sock.c:1394
 pppol2tp_create+0x33/0x1f0 net/l2tp/l2tp_ppp.c:534
 pppox_create+0xf1/0x200 drivers/net/ppp/pppox.c:121
 __sock_create+0x3ab/0x640 net/socket.c:1182
 sock_create net/socket.c:1222 [inline]
 SYSC_socket net/socket.c:1252 [inline]
 SyS_socket+0xf0/0x1b0 net/socket.c:1232
 do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 do_fast_syscall_32+0x2f5/0x870 arch/x86/entry/common.c:387
 entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137

Freed by task 4836:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:582
 slab_free_hook mm/slub.c:1355 [inline]
 slab_free_freelist_hook mm/slub.c:1377 [inline]
 slab_free mm/slub.c:2958 [inline]
 kfree+0x103/0x300 mm/slub.c:3878
 sk_prot_free net/core/sock.c:1377 [inline]
 __sk_destruct+0x47f/0x570 net/core/sock.c:1455
 sk_destruct+0x47/0x80 net/core/sock.c:1463
 __sk_free+0x57/0x230 net/core/sock.c:1471
 sk_free+0x23/0x30 net/core/sock.c:1482
 sock_put include/net/sock.h:1588 [inline]
 pppol2tp_session_sock_put+0x5a/0x70 net/l2tp/l2tp_ppp.c:271
 l2tp_tunnel_closeall+0x254/0x3a0 net/l2tp/l2tp_core.c:1371
 l2tp_udp_encap_destroy+0x87/0xe0 net/l2tp/l2tp_core.c:1394
 udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1336
 sk_common_release+0x6b/0x2f0 net/core/sock.c:2727
 udp_lib_close+0x15/0x20 include/net/udp.h:203
 inet_release+0xfa/0x1d0 net/ipv4/af_inet.c:434
 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:440
 sock_release+0x8d/0x1e0 net/socket.c:599
 sock_close+0x16/0x20 net/socket.c:1046
 __fput+0x28c/0x6e0 fs/file_table.c:208
 ____fput+0x15/0x20 fs/file_table.c:244
 task_work_run+0x115/0x190 kernel/task_work.c:116
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161
 prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 do_syscall_32_irqs_on arch/x86/entry/common.c:331 [inline]
 do_fast_syscall_32+0x5c1/0x870 arch/x86/entry/common.c:387
 entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137

The buggy address belongs to the object at ffff8801d3f99980
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 160 bytes inside of
 2048-byte region [ffff8801d3f99980, ffff8801d3f9a180)
The buggy address belongs to the page:
page:ffffea00074fe600 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x8000000000004080(slab|head)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d3f99900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d3f99980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d3f99a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff8801d3f99a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d3f99b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================