==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:102 [inline]
BUG: KASAN: use-after-free in test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:71 [inline]
BUG: KASAN: use-after-free in l2tp_session_delete+0x27/0x4e0 net/l2tp/l2tp_core.c:1561
Write of size 8 at addr ffff8881216e0808 by task kworker/u4:24/3539

CPU: 1 PID: 3539 Comm: kworker/u4:24 Not tainted 6.1.134-syzkaller-00012-g646380b087a5 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Workqueue: l2tp l2tp_tunnel_del_work
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0xee/0x150 lib/dump_stack.c:106
 print_address_description+0x71/0x210 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:427
 kasan_report+0x122/0x150 mm/kasan/report.c:531
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x280/0x290 mm/kasan/generic.c:189
 __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
 instrument_atomic_read_write include/linux/instrumented.h:102 [inline]
 test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:71 [inline]
 l2tp_session_delete+0x27/0x4e0 net/l2tp/l2tp_core.c:1561
 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1216 [inline]
 l2tp_tunnel_del_work+0x201/0x420 net/l2tp/l2tp_core.c:1256
 process_one_work+0x71f/0xc40 kernel/workqueue.c:2299
 worker_thread+0xa29/0x11f0 kernel/workqueue.c:2446
 kthread+0x281/0x320 kernel/kthread.c:386
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

Allocated by task 8126:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_alloc_info+0x25/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:379 [inline]
 __kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:388
 kasan_kmalloc include/linux/kasan.h:212 [inline]
 __do_kmalloc_node mm/slab_common.c:938 [inline]
 __kmalloc+0xb1/0x1e0 mm/slab_common.c:951
 kmalloc include/linux/slab.h:568 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 l2tp_session_create+0x38/0xbe0 net/l2tp/l2tp_core.c:1597
 pppol2tp_connect+0xb35/0x1570 net/l2tp/l2tp_ppp.c:781
 __sys_connect_file net/socket.c:2001 [inline]
 __sys_connect+0x398/0x420 net/socket.c:2018
 __do_sys_connect net/socket.c:2028 [inline]
 __se_sys_connect net/socket.c:2025 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:2025
 x64_sys_call+0x88d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 8063:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x31/0x50 mm/kasan/generic.c:516
 ____kasan_slab_free+0x132/0x180 mm/kasan/common.c:241
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:249
 kasan_slab_free include/linux/kasan.h:178 [inline]
 slab_free_hook mm/slub.c:1745 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1771
 slab_free mm/slub.c:3686 [inline]
 __kmem_cache_free+0xb7/0x1b0 mm/slub.c:3702
 kfree+0x6f/0xf0 mm/slab_common.c:990
 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
 l2tp_session_dec_refcount+0xaf/0x1a0 net/l2tp/l2tp_core.c:205
 pppol2tp_session_destruct+0xb1/0xf0 net/l2tp/l2tp_ppp.c:418
 __sk_destruct+0x64/0x600 net/core/sock.c:2148
 sk_destruct net/core/sock.c:2193 [inline]
 __sk_free+0x313/0x410 net/core/sock.c:2204
 sk_free+0x54/0x90 net/core/sock.c:2215
 sock_put include/net/sock.h:2049 [inline]
 pppol2tp_put_sk+0x7a/0xb0 net/l2tp/l2tp_ppp.c:401
 rcu_do_batch+0x515/0xb90 kernel/rcu/tree.c:2297
 rcu_core+0x5a5/0xe70 kernel/rcu/tree.c:2557
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2574
 handle_softirqs+0x1d7/0x600 kernel/softirq.c:624
 __do_softirq kernel/softirq.c:662 [inline]
 invoke_softirq kernel/softirq.c:479 [inline]
 __irq_exit_rcu+0x52/0xf0 kernel/softirq.c:711
 irq_exit_rcu+0x9/0x10 kernel/softirq.c:723
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa9/0xc0 arch/x86/kernel/apic/apic.c:1118
 asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:691

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xb6/0xc0 mm/kasan/generic.c:486
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:496
 __call_rcu_common kernel/rcu/tree.c:2807 [inline]
 call_rcu+0xd4/0xf90 kernel/rcu/tree.c:2926
 pppol2tp_release+0x208/0x2d0 net/l2tp/l2tp_ppp.c:457
 __sock_release net/socket.c:652 [inline]
 sock_close+0xf1/0x290 net/socket.c:1390
 __fput+0x1fc/0x8f0 fs/file_table.c:320
 ____fput+0x15/0x20 fs/file_table.c:348
 task_work_run+0x1db/0x240 kernel/task_work.c:203
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0x9b/0xb0 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Second to last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xb6/0xc0 mm/kasan/generic.c:486
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:496
 __call_rcu_common kernel/rcu/tree.c:2807 [inline]
 call_rcu+0xd4/0xf90 kernel/rcu/tree.c:2926
 fib6_info_release include/net/ip6_fib.h:350 [inline]
 fib6_del_route net/ipv6/ip6_fib.c:1999 [inline]
 fib6_del+0xc31/0xf50 net/ipv6/ip6_fib.c:2032
 fib6_clean_node+0x2a4/0x530 net/ipv6/ip6_fib.c:2194
 fib6_walk_continue+0x50e/0x710 net/ipv6/ip6_fib.c:2116
 fib6_walk+0x153/0x290 net/ipv6/ip6_fib.c:2164
 fib6_clean_tree net/ipv6/ip6_fib.c:2244 [inline]
 __fib6_clean_all net/ipv6/ip6_fib.c:2260 [inline]
 fib6_clean_all+0x16a/0x230 net/ipv6/ip6_fib.c:2271
 rt6_sync_down_dev net/ipv6/route.c:4924 [inline]
 rt6_disable_ip+0x11b/0x8f0 net/ipv6/route.c:4929
 addrconf_ifdown+0x15d/0x1910 net/ipv6/addrconf.c:3823
 addrconf_notify+0x39f/0xe40 net/ipv6/addrconf.c:-1
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455
 call_netdevice_notifiers_info net/core/dev.c:2009 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2047 [inline]
 call_netdevice_notifiers net/core/dev.c:2061 [inline]
 dev_close_many+0x32d/0x4d0 net/core/dev.c:1609
 unregister_netdevice_many+0x439/0x1820 net/core/dev.c:10913
 ip_tunnel_delete_nets+0x346/0x390 net/ipv4/ip_tunnel.c:1153
 erspan_exit_batch_net+0x22/0x30 net/ipv4/ip_gre.c:1723
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x62d/0xb00 net/core/net_namespace.c:604
 process_one_work+0x71f/0xc40 kernel/workqueue.c:2299
 worker_thread+0xa29/0x11f0 kernel/workqueue.c:2446
 kthread+0x281/0x320 kernel/kthread.c:386
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff8881216e0800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 8 bytes inside of
 512-byte region [ffff8881216e0800, ffff8881216e0a00)

The buggy address belongs to the physical page:
page:ffffea000485b800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1216e0
head:ffffea000485b800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004cb4400 dead000000000003 ffff888100042f00
raw: 0000000000000000 0000000080100010 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 0x152a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL), pid 346, tgid 346 (kworker/u4:4), ts 179629854441, free_ts 173082502895
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2637
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2644
 get_page_from_freelist+0x2c6e/0x2ce0 mm/page_alloc.c:4539
 __alloc_pages+0x19e/0x3a0 mm/page_alloc.c:5838
 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
 allocate_slab mm/slub.c:1962 [inline]
 new_slab+0x98/0x3d0 mm/slub.c:2015
 ___slab_alloc+0x6f6/0xb50 mm/slub.c:3203
 __slab_alloc+0x5e/0xa0 mm/slub.c:3302
 slab_alloc_node mm/slub.c:3387 [inline]
 __kmem_cache_alloc_node+0x203/0x2c0 mm/slub.c:3462
 __do_kmalloc_node mm/slab_common.c:937 [inline]
 __kmalloc+0xa1/0x1e0 mm/slab_common.c:951
 kmalloc include/linux/slab.h:568 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 fib6_info_alloc+0x34/0xe0 net/ipv6/ip6_fib.c:156
 ip6_route_info_create+0x526/0x1510 net/ipv6/route.c:3797
 ip6_route_add+0x27/0x130 net/ipv6/route.c:3893
 addrconf_prefix_route net/ipv6/addrconf.c:2465 [inline]
 addrconf_add_linklocal+0x3d4/0x620 net/ipv6/addrconf.c:3285
 addrconf_addr_gen+0x48e/0x5a0 net/ipv6/addrconf.c:3414
 addrconf_dev_config net/ipv6/addrconf.c:3459 [inline]
 addrconf_init_auto_addrs+0x95e/0xcf0 net/ipv6/addrconf.c:3537
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1545 [inline]
 free_pcp_prepare mm/page_alloc.c:1619 [inline]
 free_unref_page_prepare+0x742/0x750 mm/page_alloc.c:3581
 free_unref_page+0x8f/0x530 mm/page_alloc.c:3677
 free_the_page mm/page_alloc.c:830 [inline]
 __free_pages+0x67/0x100 mm/page_alloc.c:5927
 __free_slab+0xca/0x1a0 mm/slub.c:2039
 free_slab mm/slub.c:2054 [inline]
 discard_slab+0x29/0x40 mm/slub.c:2060
 __slab_free+0x201/0x280 mm/slub.c:3599
 do_slab_free mm/slub.c:3640 [inline]
 ___cache_free+0xbf/0xd0 mm/slub.c:3696
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0xc6/0x140 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x24/0x80 mm/kasan/common.c:310
 kasan_slab_alloc include/linux/kasan.h:202 [inline]
 slab_post_alloc_hook+0x4f/0x2d0 mm/slab.h:768
 slab_alloc_node mm/slub.c:3421 [inline]
 kmem_cache_alloc_node+0x181/0x340 mm/slub.c:3468
 __alloc_skb+0xdf/0x7e0 net/core/skbuff.c:505
 alloc_skb include/linux/skbuff.h:1290 [inline]
 mld_newpack+0x13a/0xa10 net/ipv6/mcast.c:1746
 add_grhead+0x67/0x300 net/ipv6/mcast.c:1857
 add_grec+0xf19/0x11d0 net/ipv6/mcast.c:1995

Memory state around the buggy address:
 ffff8881216e0700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881216e0780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881216e0800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff8881216e0880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881216e0900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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