syzbot

 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
kobject: kobject_add_internal failed for hci9:201 with -EEXIST, don't try to register things with the same name in the same directory.
Bluetooth: hci9: failed to register connection device
==================================================================
BUG: KASAN: slab-use-after-free in l2cap_sock_ready_cb+0xd5/0x140 net/bluetooth/l2cap_sock.c:1687
Read of size 8 at addr ffff88803623a200 by task kworker/u9:3/5847

CPU: 0 UID: 0 PID: 5847 Comm: kworker/u9:3 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: hci9 hci_rx_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 l2cap_sock_ready_cb+0xd5/0x140 net/bluetooth/l2cap_sock.c:1687
 l2cap_chan_ready net/bluetooth/l2cap_core.c:1263 [inline]
 l2cap_le_start+0xb0d/0x13b0 net/bluetooth/l2cap_core.c:1375
 l2cap_conn_ready net/bluetooth/l2cap_core.c:1628 [inline]
 l2cap_connect_cfm+0x6be/0x1040 net/bluetooth/l2cap_core.c:7304
 hci_connect_cfm+0x92/0x140 include/net/bluetooth/hci_core.h:2082
 le_conn_complete_evt+0xcd3/0x1220 net/bluetooth/hci_event.c:5771
 hci_le_conn_complete_evt+0x187/0x450 net/bluetooth/hci_event.c:5797
 hci_event_func net/bluetooth/hci_event.c:7542 [inline]
 hci_event_packet+0x78f/0x1200 net/bluetooth/hci_event.c:7599
 hci_rx_work+0x46a/0xe80 net/bluetooth/hci_core.c:4071
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 6696:
 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:388 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:405
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4376 [inline]
 __kmalloc_noprof+0x1ef/0x430 mm/slub.c:4388
 kmalloc_noprof include/linux/slab.h:909 [inline]
 sk_prot_alloc+0xe7/0x220 net/core/sock.c:2239
 sk_alloc+0x3a/0x370 net/core/sock.c:2295
 bt_sock_alloc+0x3b/0x310 net/bluetooth/af_bluetooth.c:151
 l2cap_sock_alloc net/bluetooth/l2cap_sock.c:1897 [inline]
 l2cap_sock_create+0x147/0x300 net/bluetooth/l2cap_sock.c:1939
 bt_sock_create+0x160/0x240 net/bluetooth/af_bluetooth.c:135
 __sock_create+0x4b0/0x9f0 net/socket.c:1589
 sock_create net/socket.c:1647 [inline]
 __sys_socket_create net/socket.c:1684 [inline]
 __sys_socket+0xd7/0x1b0 net/socket.c:1731
 __do_sys_socket net/socket.c:1745 [inline]
 __se_sys_socket net/socket.c:1743 [inline]
 __x64_sys_socket+0x7a/0x90 net/socket.c:1743
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6695:
 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:243 [inline]
 __kasan_slab_free+0x5b/0x80 mm/kasan/common.c:275
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2422 [inline]
 slab_free mm/slub.c:4695 [inline]
 kfree+0x195/0x550 mm/slub.c:4894
 sk_prot_free net/core/sock.c:2278 [inline]
 __sk_destruct+0x4e4/0x670 net/core/sock.c:2373
 l2cap_sock_release+0x1b0/0x230 net/bluetooth/l2cap_sock.c:1438
 __sock_release net/socket.c:649 [inline]
 sock_close+0xc3/0x240 net/socket.c:1439
 __fput+0x45b/0xa80 fs/file_table.c:468
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xec/0x110 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88803623a000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 512 bytes inside of
 freed 2048-byte region [ffff88803623a000, ffff88803623a800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88803623f000 pfn:0x36238
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 ffff888019842000 ffffea00017e3a00 0000000000000002
raw: ffff88803623f000 0000000080080007 00000000f5000000 0000000000000000
head: 0080000000000040 ffff888019842000 ffffea00017e3a00 0000000000000002
head: ffff88803623f000 0000000080080007 00000000f5000000 0000000000000000
head: 0080000000000003 ffffea0000d88e01 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 5906, tgid 5906 (kworker/1:4), ts 280186360105, free_ts 280130082200
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x2119/0x21b0 mm/page_alloc.c:3858
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5148
 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:2492 [inline]
 allocate_slab+0x8a/0x370 mm/slub.c:2660
 new_slab mm/slub.c:2714 [inline]
 ___slab_alloc+0x8d1/0xdc0 mm/slub.c:3901
 __slab_alloc mm/slub.c:3992 [inline]
 __slab_alloc_node mm/slub.c:4067 [inline]
 slab_alloc_node mm/slub.c:4228 [inline]
 __do_kmalloc_node mm/slub.c:4375 [inline]
 __kmalloc_node_track_caller_noprof+0x14c/0x450 mm/slub.c:4395
 kmalloc_reserve+0x136/0x290 net/core/skbuff.c:600
 __alloc_skb+0x142/0x2d0 net/core/skbuff.c:669
 alloc_skb include/linux/skbuff.h:1336 [inline]
 mld_newpack+0x13c/0xc40 net/ipv6/mcast.c:1780
 add_grhead+0x5a/0x2a0 net/ipv6/mcast.c:1891
 add_grec+0x1452/0x1740 net/ipv6/mcast.c:2030
 mld_send_initial_cr+0x288/0x550 net/ipv6/mcast.c:2273
 mld_dad_work+0x46/0x490 net/ipv6/mcast.c:2299
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
page last free pid 6610 tgid 6610 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 __free_frozen_pages+0xb59/0xce0 mm/page_alloc.c:2895
 discard_slab mm/slub.c:2758 [inline]
 __put_partials+0x159/0x1a0 mm/slub.c:3223
 __slab_free+0x2b3/0x390 mm/slub.c:4565
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:340
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4191 [inline]
 slab_alloc_node mm/slub.c:4240 [inline]
 kmem_cache_alloc_noprof+0x143/0x310 mm/slub.c:4247
 vm_area_dup+0x2b/0x670 mm/vma_init.c:122
 __split_vma+0x1ad/0x9e0 mm/vma.c:515
 vms_gather_munmap_vmas+0x4ce/0x12f0 mm/vma.c:1380
 __mmap_prepare mm/vma.c:2359 [inline]
 __mmap_region mm/vma.c:2651 [inline]
 mmap_region+0x729/0x20a0 mm/vma.c:2739
 do_mmap+0xc23/0x10c0 mm/mmap.c:558
 vm_mmap_pgoff+0x2a9/0x4d0 mm/util.c:580
 ksys_mmap_pgoff+0x4e9/0x720 mm/mmap.c:604
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88803623a100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803623a180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88803623a200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88803623a280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803623a300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================