KASAN: use-after-free Read in bt_accept_unlink (3)

Status: upstream: reported on 2026/10/21 10:53
Reported-by: syzbot+3c58fa252dc8841d100d@syzkaller.appspotmail.com
First crash: 2d12h, last: 2d12h
▶ ▼ Similar bugs (11)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: use-after-free Read in bt_accept_unlink 19 1 499d 499d 0/3 auto-obsoleted due to no activity on 2025/09/18 23:51
linux-5.15 KASAN: use-after-free Read in bt_accept_unlink 19 1 265d 265d 0/3 auto-obsoleted due to no activity on 2026/05/11 03:38
linux-6.1 KASAN: slab-out-of-bounds Read in bt_accept_unlink 19 20 50d 300d 0/3 upstream: reported on 2025/12/27 18:50
upstream KASAN: slab-use-after-free Read in bt_accept_unlink bluetooth 19 syz 250 52d 732d 0/29 upstream: reported syz repro on 2024/10/21 08:47
linux-5.15 KASAN: use-after-free Read in bt_accept_unlink (2) 19 1 145d 145d 0/3 auto-obsoleted due to no activity on 2026/09/08 07:00
linux-6.6 KASAN: slab-use-after-free Read in bt_accept_unlink (2) 19 4 46d 109d 0/2 upstream: reported on 2026/07/06 20:50
linux-5.15 BUG: corrupted list in bt_accept_unlink 17 3 522d 562d 0/3 auto-obsoleted due to no activity on 2025/08/27 17:34
linux-6.6 KASAN: slab-out-of-bounds Read in bt_accept_unlink 17 1 493d 493d 0/2 auto-obsoleted due to no activity on 2025/09/25 00:09
upstream general protection fault in bt_accept_unlink (2) bluetooth 2 1 2060d 2056d 0/29 auto-closed as invalid on 2021/07/01 06:33
linux-6.6 KASAN: slab-use-after-free Read in bt_accept_unlink 19 1 385d 385d 0/2 auto-obsoleted due to no activity on 2026/01/11 02:55
linux-5.15 KASAN: slab-out-of-bounds Read in bt_accept_unlink 17 1 381d 381d 0/3 auto-obsoleted due to no activity on 2026/01/15 10:51

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x106/0x7d40 kernel/locking/lockdep.c:4985
Read of size 8 at addr ffff888024ae3548 by task kworker/1:5/4289

CPU: 1 PID: 4289 Comm: kworker/1:5 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Workqueue: events l2cap_chan_timeout

Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 __lock_acquire+0x106/0x7d40 kernel/locking/lockdep.c:4985
 lock_acquire+0x19f/0x400 kernel/locking/lockdep.c:5737
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
 _raw_spin_lock_bh+0x32/0x50 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:369 [inline]
 bt_accept_unlink+0x5f/0x290 net/bluetooth/af_bluetooth.c:260
 l2cap_sock_teardown_cb+0x1af/0x380 net/bluetooth/l2cap_sock.c:1622
 l2cap_chan_del+0x8f/0x640 net/bluetooth/l2cap_core.c:663
 l2cap_chan_close+0x566/0x800 net/bluetooth/l2cap_core.c:862
 l2cap_chan_timeout+0x200/0x370 net/bluetooth/l2cap_core.c:460
 process_one_work+0x867/0xff0 kernel/workqueue.c:2310
 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Allocated by task 3851:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc mm/kasan/common.c:513 [inline]
 __kasan_kmalloc+0xaf/0xe0 mm/kasan/common.c:522
 kmalloc include/linux/slab.h:612 [inline]
 sk_prot_alloc+0xe7/0x210 net/core/sock.c:1865
 sk_alloc+0x2f/0x310 net/core/sock.c:1921
 __netlink_create+0x6c/0x290 net/netlink/af_netlink.c:629
 netlink_create+0x3a7/0x510 net/netlink/af_netlink.c:688
 __sock_create+0x473/0x910 net/socket.c:1496
 sock_create net/socket.c:1552 [inline]
 __sys_socket+0xe2/0x170 net/socket.c:1594
 __do_sys_socket net/socket.c:1603 [inline]
 __se_sys_socket net/socket.c:1601 [inline]
 __x64_sys_socket+0x76/0x80 net/socket.c:1601
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 4173:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xec/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kfree+0xef/0x2a0 mm/slub.c:4564
 sk_prot_free net/core/sock.c:1904 [inline]
 __sk_destruct+0x580/0x840 net/core/sock.c:1990
 rcu_do_batch kernel/rcu/tree.c:2523 [inline]
 rcu_core+0x96e/0x1650 kernel/rcu/tree.c:2763
 handle_softirqs+0x336/0x830 kernel/softirq.c:576
 do_softirq+0x142/0x210 kernel/softirq.c:477
 __local_bh_enable_ip+0x180/0x1c0 kernel/softirq.c:401
 spin_unlock_bh include/linux/spinlock.h:409 [inline]
 nf_conntrack_tcp_packet+0x2453/0x60a0 net/netfilter/nf_conntrack_proto_tcp.c:1235
 nf_conntrack_handle_packet net/netfilter/nf_conntrack_core.c:1900 [inline]
 nf_conntrack_in+0xbd6/0x17b0 net/netfilter/nf_conntrack_core.c:1991
 nf_hook_entry_hookfn include/linux/netfilter.h:142 [inline]
 nf_hook_slow+0xb9/0x200 net/netfilter/core.c:584
 nf_hook+0x205/0x360 include/linux/netfilter.h:257
 __ip_local_out+0x4b7/0x5e0 net/ipv4/ip_output.c:115
 ip_local_out net/ipv4/ip_output.c:124 [inline]
 __ip_queue_xmit+0x1120/0x1c60 net/ipv4/ip_output.c:538
 __tcp_transmit_skb+0x1ca3/0x31e0 net/ipv4/tcp_output.c:1404
 tcp_transmit_skb net/ipv4/tcp_output.c:1422 [inline]
 tcp_write_xmit+0x1a8d/0x65c0 net/ipv4/tcp_output.c:2718
 __tcp_push_pending_frames+0x92/0x250 net/ipv4/tcp_output.c:2903
 tcp_push_pending_frames include/net/tcp.h:1918 [inline]
 tcp_data_snd_check net/ipv4/tcp_input.c:5572 [inline]
 tcp_rcv_established+0xbbd/0x1de0 net/ipv4/tcp_input.c:6069
 tcp_v4_do_rcv+0x435/0x9b0 net/ipv4/tcp_ipv4.c:1738
 sk_backlog_rcv include/net/sock.h:1080 [inline]
 __release_sock+0x1e6/0x460 net/core/sock.c:2730
 release_sock+0x5b/0x1b0 net/core/sock.c:3273
 tcp_sendmsg+0x35/0x40 net/ipv4/tcp.c:1461
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 sock_write_iter+0x2a6/0x3a0 net/socket.c:1090
 call_write_iter include/linux/fs.h:2179 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x748/0xd70 fs/read_write.c:594
 ksys_write+0x153/0x260 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Last potentially related work creation:
 kasan_save_stack+0x35/0x60 mm/kasan/common.c:38
 kasan_record_aux_stack+0xb8/0x100 mm/kasan/generic.c:348
 __call_rcu kernel/rcu/tree.c:3011 [inline]
 call_rcu+0x189/0x900 kernel/rcu/tree.c:3091
 netlink_release+0x134c/0x1790 net/netlink/af_netlink.c:795
 __sock_release net/socket.c:651 [inline]
 sock_close+0xbf/0x210 net/socket.c:1346
 __fput+0x212/0x8c0 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:184
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:217
 __syscall_exit_to_user_mode_work kernel/entry/common.c:299 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:310
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff888024ae3000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1352 bytes inside of
 2048-byte region [ffff888024ae3000, ffff888024ae3800)
The buggy address belongs to the page:
page:ffffea000092b800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x24ae0
head:ffffea000092b800 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888017842000
raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000
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 4186, ts 69401570137, free_ts 69311038473
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x24f6/0x2670 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
 alloc_slab_page mm/slub.c:1780 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x807/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 __kmalloc_track_caller+0x11b/0x330 mm/slub.c:4930
 kmemdup+0x22/0x50 mm/util.c:128
 neigh_sysctl_register+0xab/0xa90 net/core/neighbour.c:3652
 addrconf_sysctl_register+0xac/0x1b0 net/ipv6/addrconf.c:7172
 ipv6_add_dev+0xbfb/0x11a0 net/ipv6/addrconf.c:454
 ipv6_find_idev+0xbd/0x1d0 net/ipv6/addrconf.c:490
 inet6_rtm_newaddr+0x460/0x8f0 net/ipv6/addrconf.c:4950
 rtnetlink_rcv_msg+0x7f1/0xf10 net/core/rtnetlink.c:5698
 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2519
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 __sys_sendto+0x46d/0x620 net/socket.c:2073
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
 free_slab mm/slub.c:2020 [inline]
 discard_slab mm/slub.c:2026 [inline]
 __unfreeze_partials+0x188/0x1e0 mm/slub.c:2512
 put_cpu_partial+0x12d/0x190 mm/slub.c:2592
 qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xc0 mm/kasan/common.c:444
 kasan_slab_alloc include/linux/kasan.h:254 [inline]
 slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
 slab_alloc_node mm/slub.c:3225 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x15d/0x280 mm/slub.c:3238
 getname_flags+0xb7/0x4f0 fs/namei.c:138
 do_sys_openat2+0xdd/0x500 fs/open.c:1249
 do_sys_open fs/open.c:1271 [inline]
 __do_sys_openat fs/open.c:1287 [inline]
 __se_sys_openat fs/open.c:1282 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1282
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff888024ae3400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888024ae3480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888024ae3500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff888024ae3580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888024ae3600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/21 10:52 linux-5.15.y 792fbe1537d8 61c200c7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in bt_accept_unlink
* Struck through repros no longer work on HEAD.