==================================================================
BUG: KASAN: slab-use-after-free in rt_spin_lock+0x83/0x400 kernel/locking/spinlock_rt.c:56
Read of size 1 at addr ffff8880661ba7e8 by task syz-executor/15500

CPU: 0 UID: 0 PID: 15500 Comm: syz-executor Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 __kasan_check_byte+0x2a/0x40 mm/kasan/common.c:574
 kasan_check_byte include/linux/kasan.h:402 [inline]
 lock_acquire+0x84/0x350 kernel/locking/lockdep.c:5844
 rt_spin_lock+0x83/0x400 kernel/locking/spinlock_rt.c:56
 spin_lock_bh include/linux/spinlock_rt.h:90 [inline]
 bt_accept_unlink+0x7d/0x2f0 net/bluetooth/af_bluetooth.c:262
 l2cap_sock_teardown_cb+0x17e/0x490 net/bluetooth/l2cap_sock.c:1692
 l2cap_chan_del+0x98/0x600 net/bluetooth/l2cap_core.c:659
 l2cap_conn_del+0x343/0x570 net/bluetooth/l2cap_core.c:1803
 hci_disconn_cfm include/net/bluetooth/hci_core.h:2151 [inline]
 hci_conn_hash_flush+0x105/0x260 net/bluetooth/hci_conn.c:2733
 hci_dev_close_sync+0x7fc/0x10a0 net/bluetooth/hci_sync.c:5405
 hci_dev_do_close net/bluetooth/hci_core.c:499 [inline]
 hci_unregister_dev+0x232/0x5b0 net/bluetooth/hci_core.c:2678
 vhci_release+0x170/0x1c0 drivers/bluetooth/hci_vhci.c:700
 __fput+0x42a/0xa80 fs/file_table.c:512
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x73a/0x2360 kernel/exit.c:1004
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1147
 get_signal+0x121b/0x12c0 kernel/signal.c:3038
 arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x104/0x730 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x353/0x580 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f10a84d57f3
Code: Unable to access opcode bytes at 0x7f10a84d57c9.
RSP: 002b:00007ffe967ecc98 EFLAGS: 00000293 ORIG_RAX: 00000000000000d9
RAX: 0000000000000000 RBX: 0000555566c9fa10 RCX: 00007f10a84d57f3
RDX: 0000000000008000 RSI: 0000555566c9fa40 RDI: 0000000000000003
RBP: 0000555566c9fa40 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000555566c9fa14
R13: ffffffffffffffe8 R14: 0000000000000002 R15: 00007ffe967ecd60
 </TASK>

Allocated by task 20004:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5362 [inline]
 __kmalloc_noprof+0x41a/0x780 mm/slub.c:5387
 _kmalloc_noprof include/linux/slab.h:973 [inline]
 sk_prot_alloc+0xe7/0x210 net/core/sock.c:2252
 sk_alloc+0x3a/0x390 net/core/sock.c:2308
 bt_sock_alloc+0x3b/0x340 net/bluetooth/af_bluetooth.c:148
 l2cap_sock_alloc net/bluetooth/l2cap_sock.c:1983 [inline]
 l2cap_sock_create+0x147/0x330 net/bluetooth/l2cap_sock.c:2025
 bt_sock_create+0x163/0x240 net/bluetooth/af_bluetooth.c:132
 __sock_create+0x4e8/0x960 net/socket.c:1666
 sock_create net/socket.c:1724 [inline]
 __sys_socket_create net/socket.c:1761 [inline]
 __sys_socket+0xd9/0x320 net/socket.c:1808
 __do_sys_socket net/socket.c:1822 [inline]
 __se_sys_socket net/socket.c:1820 [inline]
 __x64_sys_socket+0x7a/0x90 net/socket.c:1820
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 20003:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2705 [inline]
 slab_free mm/slub.c:6405 [inline]
 kfree+0x1c5/0x6c0 mm/slub.c:6720
 sk_prot_free net/core/sock.c:2291 [inline]
 __sk_destruct+0x754/0x9e0 net/core/sock.c:2391
 l2cap_sock_release+0x1b3/0x250 net/bluetooth/l2cap_sock.c:1478
 __sock_release+0xa0/0x1f0 net/socket.c:714
 sock_close+0x1c/0x30 net/socket.c:1516
 __fput+0x42a/0xa80 fs/file_table.c:512
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
 exit_to_user_mode_loop+0x1fa/0x730 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x353/0x580 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880661ba000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 2024 bytes inside of
 freed 4096-byte region [ffff8880661ba000, ffff8880661bb000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x661b8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88813fe24140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88813fe24140 dead000000000100 dead000000000122
head: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
head: 0080000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5270, tgid 5270 (dhcpcd), ts 1077035012405, free_ts 1077011075835
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0x2639/0x26b0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3294 [inline]
 allocate_slab+0x79/0x5e0 mm/slub.c:3408
 new_slab mm/slub.c:3454 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7338
 refill_sheaf mm/slub.c:2832 [inline]
 __pcs_replace_empty_main+0x330/0x690 mm/slub.c:4703
 alloc_from_pcs mm/slub.c:4801 [inline]
 slab_alloc_node mm/slub.c:4933 [inline]
 __kmalloc_cache_node_noprof+0x50a/0x6a0 mm/slub.c:5530
 _kmalloc_node_noprof include/linux/slab.h:1174 [inline]
 page_pool_create_percpu+0x73/0xc90 net/core/page_pool.c:346
 nsim_create_page_pool drivers/net/netdevsim/netdev.c:430 [inline]
 nsim_init_napi drivers/net/netdevsim/netdev.c:453 [inline]
 nsim_open+0x3ca/0xa10 drivers/net/netdevsim/netdev.c:509
 __dev_open+0x46f/0x850 net/core/dev.c:1702
 __dev_change_flags+0x329/0x820 net/core/dev.c:9755
 netif_change_flags+0x7c/0x1b0 net/core/dev.c:9818
 dev_change_flags+0x128/0x260 net/core/dev_api.c:68
 devinet_ioctl+0x966/0x1c50 net/ipv4/devinet.c:1199
 inet_ioctl+0x42a/0x560 net/ipv4/af_inet.c:1009
 sock_do_ioctl+0x101/0x320 net/socket.c:1315
page last free pid 14942 tgid 14942 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0x10de/0x11c0 mm/page_alloc.c:2950
 __slab_free+0x252/0x2a0 mm/slub.c:5767
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_kmalloc+0x22/0xb0 mm/kasan/common.c:406
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5362 [inline]
 __kvmalloc_node_noprof+0x5be/0x8a0 mm/slub.c:6933
 alloc_netdev_mqs+0xa9/0x12c0 net/core/dev.c:12061
 __ip_tunnel_create+0x348/0x560 net/ipv4/ip_tunnel.c:255
 ip_tunnel_init_net+0x2e5/0x820 net/ipv4/ip_tunnel.c:1150
 ops_init+0x35d/0x5d0 net/core/net_namespace.c:137
 setup_net+0x118/0x350 net/core/net_namespace.c:446
 copy_net_ns+0x4f9/0x720 net/core/net_namespace.c:579
 create_new_namespaces+0x3f0/0x6b0 kernel/nsproxy.c:132
 unshare_nsproxy_namespaces+0x149/0x190 kernel/nsproxy.c:234
 ksys_unshare+0x57d/0xa00 kernel/fork.c:3268
 __do_sys_unshare kernel/fork.c:3342 [inline]
 __se_sys_unshare kernel/fork.c:3340 [inline]
 __x64_sys_unshare+0x38/0x50 kernel/fork.c:3340

Memory state around the buggy address:
 ffff8880661ba680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880661ba700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880661ba780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff8880661ba800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880661ba880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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