==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:70 [inline]
BUG: KASAN: use-after-free in l2tp_session_delete+0x24/0x4e0 net/l2tp/l2tp_core.c:1563
Write of size 8 at addr ffff888127a33808 by task kworker/u4:7/586

CPU: 1 PID: 586 Comm: kworker/u4:7 Not tainted 5.15.176-syzkaller-00972-g829d9f138569 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Workqueue: l2tp l2tp_tunnel_del_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1c0 lib/dump_stack.c:106
 print_address_description+0x87/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x179/0x1c0 mm/kasan/report.c:444
 kasan_check_range+0x293/0x2a0 mm/kasan/generic.c:189
 __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:70 [inline]
 l2tp_session_delete+0x24/0x4e0 net/l2tp/l2tp_core.c:1563
 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1218 [inline]
 l2tp_tunnel_del_work+0x19d/0x380 net/l2tp/l2tp_core.c:1258
 process_one_work+0x6bb/0xc10 kernel/workqueue.c:2325
 worker_thread+0xad5/0x12a0 kernel/workqueue.c:2472
 kthread+0x421/0x510 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Allocated by task 2964:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:433 [inline]
 ____kasan_kmalloc+0xdb/0x110 mm/kasan/common.c:512
 __kasan_kmalloc+0x9/0x10 mm/kasan/common.c:521
 kasan_kmalloc include/linux/kasan.h:227 [inline]
 __kmalloc+0x13f/0x2c0 mm/slub.c:4431
 kmalloc include/linux/slab.h:608 [inline]
 kzalloc include/linux/slab.h:733 [inline]
 l2tp_session_create+0x38/0xb60 net/l2tp/l2tp_core.c:1599
 pppol2tp_connect+0xc5d/0x1690 net/l2tp/l2tp_ppp.c:782
 __sys_connect_file net/socket.c:1923 [inline]
 __sys_connect+0x38b/0x410 net/socket.c:1940
 __do_sys_connect net/socket.c:1950 [inline]
 __se_sys_connect net/socket.c:1947 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:1947
 x64_sys_call+0x14e/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 278:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x126/0x160 mm/kasan/common.c:365
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1723 [inline]
 slab_free_freelist_hook+0xbd/0x190 mm/slub.c:1749
 slab_free mm/slub.c:3521 [inline]
 kfree+0xcc/0x270 mm/slub.c:4583
 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
 l2tp_session_dec_refcount+0xa9/0x1b0 net/l2tp/l2tp_core.c:205
 pppol2tp_session_destruct+0xaf/0xf0 net/l2tp/l2tp_ppp.c:419
 __sk_destruct+0x56/0x5b0 net/core/sock.c:1964
 sk_destruct net/core/sock.c:2009 [inline]
 __sk_free+0x36c/0x470 net/core/sock.c:2020
 sk_free+0x51/0x80 net/core/sock.c:2031
 sock_put include/net/sock.h:1929 [inline]
 pppol2tp_put_sk+0x77/0xb0 net/l2tp/l2tp_ppp.c:402
 rcu_do_batch+0x57a/0xc10 kernel/rcu/tree.c:2523
 rcu_core+0x517/0x1020 kernel/rcu/tree.c:2763
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776
 handle_softirqs+0x25e/0x5c0 kernel/softirq.c:565
 __do_softirq+0xb/0xd kernel/softirq.c:603

Last potentially related work creation:
 kasan_save_stack+0x3b/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd3/0xf0 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu_common kernel/rcu/tree.c:3007 [inline]
 call_rcu+0x123/0x10b0 kernel/rcu/tree.c:3125
 pppol2tp_release+0x20f/0x2d0 net/l2tp/l2tp_ppp.c:458
 __sock_release net/socket.c:649 [inline]
 sock_close+0xdf/0x270 net/socket.c:1336
 __fput+0x228/0x8c0 fs/file_table.c:280
 ____fput+0x15/0x20 fs/file_table.c:308
 task_work_run+0x129/0x190 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0xc4/0xe0 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x26/0x160 kernel/entry/common.c:307
 do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Second to last potentially related work creation:
 kasan_save_stack+0x3b/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd3/0xf0 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu_common kernel/rcu/tree.c:3007 [inline]
 call_rcu+0x123/0x10b0 kernel/rcu/tree.c:3125
 pwq_unbound_release_workfn+0x29f/0x2e0
 process_one_work+0x6bb/0xc10 kernel/workqueue.c:2325
 worker_thread+0xad5/0x12a0 kernel/workqueue.c:2472
 kthread+0x421/0x510 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

The buggy address belongs to the object at ffff888127a33800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 8 bytes inside of
 512-byte region [ffff888127a33800, ffff888127a33a00)
The buggy address belongs to the page:
page:ffffea00049e8c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x127a30
head:ffffea00049e8c00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100042f00
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 288, ts 23092020854, free_ts 0
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2605
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2611
 get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4485
 __alloc_pages+0x27e/0x8f0 mm/page_alloc.c:5780
 allocate_slab mm/slub.c:1932 [inline]
 new_slab+0x9a/0x4e0 mm/slub.c:1995
 ___slab_alloc+0x39e/0x830 mm/slub.c:3028
 __slab_alloc+0x4a/0x90 mm/slub.c:3115
 slab_alloc_node mm/slub.c:3206 [inline]
 slab_alloc mm/slub.c:3250 [inline]
 __kmalloc+0x172/0x2c0 mm/slub.c:4427
 kmalloc include/linux/slab.h:608 [inline]
 kzalloc include/linux/slab.h:733 [inline]
 fib6_info_alloc+0x33/0xe0 net/ipv6/ip6_fib.c:155
 ip6_route_info_create+0x50b/0x14c0 net/ipv6/route.c:3778
 addrconf_f6i_alloc+0x215/0x4c0 net/ipv6/route.c:4576
 ipv6_add_addr+0x44e/0xd40 net/ipv6/addrconf.c:1123
 inet6_addr_add+0x45a/0x9b0 net/ipv6/addrconf.c:3019
 inet6_rtm_newaddr+0x98d/0x26b0 net/ipv6/addrconf.c:4974
 rtnetlink_rcv_msg+0x951/0xc40 net/core/rtnetlink.c:5647
 netlink_rcv_skb+0x1cf/0x410 net/netlink/af_netlink.c:2493
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888127a33700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888127a33780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888127a33800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff888127a33880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888127a33900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 586 at lib/refcount.c:28 refcount_warn_saturate+0x158/0x1a0 lib/refcount.c:28
Modules linked in:
CPU: 0 PID: 586 Comm: kworker/u4:7 Tainted: G    B             5.15.176-syzkaller-00972-g829d9f138569 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Workqueue: l2tp l2tp_tunnel_del_work
RIP: 0010:refcount_warn_saturate+0x158/0x1a0 lib/refcount.c:28
Code: 04 01 48 c7 c7 a0 10 a3 85 e8 84 8d db fe 0f 0b eb 8b e8 cb 47 0a ff c6 05 d9 6e c0 04 01 48 c7 c7 00 11 a3 85 e8 68 8d db fe <0f> 0b e9 6c ff ff ff e8 ac 47 0a ff c6 05 bb 6e c0 04 01 48 c7 c7
RSP: 0018:ffffc90000c57c20 EFLAGS: 00010246
RAX: 61209661b2569e00 RBX: 0000000000000003 RCX: ffff888118af62c0
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc90000c57c30 R08: ffffffff8157a565 R09: ffffed103ee04e93
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff11024f46725
R13: 0000000000000000 R14: 0000000000000003 R15: ffff888127a33888
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c26b9b3 CR3: 0000000124fc5000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __refcount_sub_and_test include/linux/refcount.h:283 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 l2tp_session_dec_refcount+0xc4/0x1b0 net/l2tp/l2tp_core.c:204
 l2tp_session_delete+0x3bc/0x4e0 net/l2tp/l2tp_core.c:1572
 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1218 [inline]
 l2tp_tunnel_del_work+0x19d/0x380 net/l2tp/l2tp_core.c:1258
 process_one_work+0x6bb/0xc10 kernel/workqueue.c:2325
 worker_thread+0xad5/0x12a0 kernel/workqueue.c:2472
 kthread+0x421/0x510 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
---[ end trace d6faf1ae0bdf4051 ]---