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kobject: kobject_add_internal failed for hci4:201 with -EEXIST, don't try to register things with the same name in the same directory.
Bluetooth: hci4: failed to register connection device
==================================================================
BUG: KASAN: slab-use-after-free in l2cap_sock_new_connection_cb+0x1f9/0x2b0 net/bluetooth/l2cap_sock.c:1497
Read of size 8 at addr ffff8880487cd588 by task kworker/u9:1/14723

CPU: 0 UID: 0 PID: 14723 Comm: kworker/u9:1 Not tainted 6.15.0-rc6-syzkaller-00052-g9f35e33144ae #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: hci4 hci_rx_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0xb4/0x290 mm/kasan/report.c:521
 kasan_report+0x118/0x150 mm/kasan/report.c:634
 l2cap_sock_new_connection_cb+0x1f9/0x2b0 net/bluetooth/l2cap_sock.c:1497
 l2cap_connect_cfm+0x37a/0x1040 net/bluetooth/l2cap_core.c:7262
 hci_connect_cfm+0x95/0x140 include/net/bluetooth/hci_core.h:2052
 le_conn_complete_evt+0xcd3/0x1220 net/bluetooth/hci_event.c:5779
 hci_le_conn_complete_evt+0x187/0x450 net/bluetooth/hci_event.c:5805
 hci_event_func net/bluetooth/hci_event.c:7483 [inline]
 hci_event_packet+0x7a5/0x1270 net/bluetooth/hci_event.c:7538
 hci_rx_work+0x46a/0xe80 net/bluetooth/hci_core.c:4020
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xade/0x17a0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x711/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x4e/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 14723:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_noprof+0x27a/0x4f0 mm/slub.c:4339
 kmalloc_noprof include/linux/slab.h:909 [inline]
 sk_prot_alloc+0xe7/0x220 net/core/sock.c:2198
 sk_alloc+0x3a/0x370 net/core/sock.c:2254
 bt_sock_alloc+0x3b/0x310 net/bluetooth/af_bluetooth.c:148
 l2cap_sock_alloc net/bluetooth/l2cap_sock.c:1891 [inline]
 l2cap_sock_new_connection_cb+0xe2/0x2b0 net/bluetooth/l2cap_sock.c:1482
 l2cap_connect_cfm+0x37a/0x1040 net/bluetooth/l2cap_core.c:7262
 hci_connect_cfm+0x95/0x140 include/net/bluetooth/hci_core.h:2052
 le_conn_complete_evt+0xcd3/0x1220 net/bluetooth/hci_event.c:5779
 hci_le_conn_complete_evt+0x187/0x450 net/bluetooth/hci_event.c:5805
 hci_event_func net/bluetooth/hci_event.c:7483 [inline]
 hci_event_packet+0x7a5/0x1270 net/bluetooth/hci_event.c:7538
 hci_rx_work+0x46a/0xe80 net/bluetooth/hci_core.c:4020
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xade/0x17a0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x711/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x4e/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 19331:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x62/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2380 [inline]
 slab_free mm/slub.c:4642 [inline]
 kfree+0x193/0x440 mm/slub.c:4841
 sk_prot_free net/core/sock.c:2237 [inline]
 __sk_destruct+0x4e1/0x660 net/core/sock.c:2332
 l2cap_sock_cleanup_listen+0xda/0x3e0 net/bluetooth/l2cap_sock.c:1462
 l2cap_sock_release+0x5d/0x1d0 net/bluetooth/l2cap_sock.c:1425
 __sock_release net/socket.c:647 [inline]
 sock_close+0xc3/0x240 net/socket.c:1391
 __fput+0x44c/0xa70 fs/file_table.c:465
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 get_signal+0x11c5/0x1310 kernel/signal.c:2807
 arch_do_signal_or_restart+0x95/0x780 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x8b/0x120 kernel/entry/common.c:218
 do_syscall_64+0x103/0x210 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880487cd000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1416 bytes inside of
 freed 2048-byte region [ffff8880487cd000, ffff8880487cd800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x487c8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801a042000 ffffea00015a8e00 dead000000000002
raw: 0000000000000000 0000000000080008 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801a042000 ffffea00015a8e00 dead000000000002
head: 0000000000000000 0000000000080008 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea000121f201 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 10252, tgid 10252 (syz-executor), ts 614267498765, free_ts 613780614906
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1d8/0x230 mm/page_alloc.c:1718
 prep_new_page mm/page_alloc.c:1726 [inline]
 get_page_from_freelist+0x21ce/0x22b0 mm/page_alloc.c:3688
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4970
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2301
 alloc_slab_page mm/slub.c:2450 [inline]
 allocate_slab+0x8a/0x3b0 mm/slub.c:2618
 new_slab mm/slub.c:2672 [inline]
 ___slab_alloc+0xbfc/0x1480 mm/slub.c:3858
 __slab_alloc mm/slub.c:3948 [inline]
 __slab_alloc_node mm/slub.c:4023 [inline]
 slab_alloc_node mm/slub.c:4184 [inline]
 __do_kmalloc_node mm/slub.c:4326 [inline]
 __kmalloc_node_track_caller_noprof+0x2f8/0x4e0 mm/slub.c:4346
 kmalloc_reserve+0x136/0x290 net/core/skbuff.c:599
 pskb_expand_head+0x18f/0x1290 net/core/skbuff.c:2247
 netlink_trim+0x1d5/0x2e0 net/netlink/af_netlink.c:1295
 netlink_broadcast_filtered+0x80/0x1140 net/netlink/af_netlink.c:1501
 nlmsg_multicast_filtered include/net/netlink.h:1129 [inline]
 nlmsg_multicast include/net/netlink.h:1148 [inline]
 nlmsg_notify+0xf0/0x1a0 net/netlink/af_netlink.c:2577
 __dev_notify_flags+0xf4/0x2e0 net/core/dev.c:9389
 netif_change_flags+0xe8/0x1a0 net/core/dev.c:9422
 dev_change_flags+0x130/0x260 net/core/dev_api.c:68
 devinet_ioctl+0xbb4/0x1b50 net/ipv4/devinet.c:1200
page last free pid 10673 tgid 10670 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1262 [inline]
 __free_frozen_pages+0xb0e/0xcd0 mm/page_alloc.c:2725
 discard_slab mm/slub.c:2716 [inline]
 __put_partials+0x161/0x1c0 mm/slub.c:3185
 put_cpu_partial+0x17c/0x250 mm/slub.c:3260
 __slab_free+0x2f7/0x400 mm/slub.c:4512
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4147 [inline]
 slab_alloc_node mm/slub.c:4196 [inline]
 kmem_cache_alloc_noprof+0x1c1/0x3c0 mm/slub.c:4203
 ptlock_alloc+0x20/0x70 mm/memory.c:7354
 ptlock_init include/linux/mm.h:3074 [inline]
 pagetable_pte_ctor include/linux/mm.h:3122 [inline]
 __pte_alloc_one_noprof include/asm-generic/pgalloc.h:73 [inline]
 pte_alloc_one+0x6d/0x160 arch/x86/mm/pgtable.c:17
 __pte_alloc+0x25/0x160 mm/memory.c:430
 do_anonymous_page mm/memory.c:4968 [inline]
 do_pte_missing mm/memory.c:4158 [inline]
 handle_pte_fault mm/memory.c:5997 [inline]
 __handle_mm_fault+0x49e9/0x5380 mm/memory.c:6140
 handle_mm_fault+0x3f6/0x8c0 mm/memory.c:6309
 do_user_addr_fault+0x764/0x1390 arch/x86/mm/fault.c:1388
 handle_page_fault arch/x86/mm/fault.c:1480 [inline]
 exc_page_fault+0x68/0x110 arch/x86/mm/fault.c:1538
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

Memory state around the buggy address:
 ffff8880487cd480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880487cd500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880487cd580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff8880487cd600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880487cd680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================