KASAN: use-after-free Read in bt_accept_unlink (2)

Status: upstream: reported on 2026/05/31 07:00
Reported-by: syzbot+6ece52694d0954fa3a8d@syzkaller.appspotmail.com
First crash: 57d, last: 57d
▶ ▼ Similar bugs (10)
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 412d 412d 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 177d 177d 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 7 26d 212d 0/3 upstream: reported on 2025/12/27 18:50
upstream KASAN: slab-use-after-free Read in bt_accept_unlink bluetooth 19 syz 209 4d05h 644d 0/29 upstream: reported syz repro on 2024/10/21 08:47
linux-6.6 KASAN: slab-use-after-free Read in bt_accept_unlink (2) 19 1 21d 21d 0/2 upstream: reported on 2026/07/06 20:50
linux-5.15 BUG: corrupted list in bt_accept_unlink 17 3 434d 474d 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 406d 406d 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 1972d 1968d 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 297d 297d 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 293d 293d 0/3 auto-obsoleted due to no activity on 2026/01/15 10:51

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in __list_del_entry_valid+0x80/0x120 lib/list_debug.c:59
Read of size 8 at addr ffff88805f167520 by task syz.6.333/6459

CPU: 0 PID: 6459 Comm: syz.6.333 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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
 __list_del_entry_valid+0x80/0x120 lib/list_debug.c:59
 __list_del_entry include/linux/list.h:132 [inline]
 list_del_init include/linux/list.h:204 [inline]
 bt_accept_unlink+0x35/0x230 net/bluetooth/af_bluetooth.c:209
 l2cap_sock_teardown_cb+0x1af/0x380 net/bluetooth/l2cap_sock.c:1591
 l2cap_chan_del+0xab/0x620 net/bluetooth/l2cap_core.c:656
 l2cap_conn_del+0x3c1/0x6a0 net/bluetooth/l2cap_core.c:1931
 hci_disconn_cfm include/net/bluetooth/hci_core.h:1520 [inline]
 hci_conn_hash_flush+0x107/0x220 net/bluetooth/hci_conn.c:1622
 hci_dev_do_close+0x991/0x1030 net/bluetooth/hci_core.c:1795
 hci_unregister_dev+0x2d7/0x580 net/bluetooth/hci_core.c:4044
 vhci_release+0x73/0xc0 drivers/bluetooth/hci_vhci.c:345
 __fput+0x234/0x930 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0x626/0x20c0 kernel/exit.c:884
 do_group_exit+0x12e/0x300 kernel/exit.c:998
 get_signal+0x6d6/0x12d0 kernel/signal.c:2900
 arch_do_signal_or_restart+0xe7/0x12c0 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7faced966e59
Code: Unable to access opcode bytes at RIP 0x7faced966e2f.
RSP: 002b:00007facebb9f028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: 000000000003e740 RBX: 00007facedbe0090 RCX: 00007faced966e59
RDX: 00000000fffffe66 RSI: 0000200000002940 RDI: 0000000000000004
RBP: 00007faced9fcd6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007facedbe0128 R14: 00007facedbe0090 R15: 00007ffcab6f2788
 </TASK>

Allocated by task 5908:
 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+0xb5/0xf0 mm/kasan/common.c:522
 kmalloc include/linux/slab.h:612 [inline]
 sk_prot_alloc+0xe7/0x210 net/core/sock.c:1866
 sk_alloc+0x2f/0x310 net/core/sock.c:1922
 l2cap_sock_alloc+0x33/0x200 net/bluetooth/l2cap_sock.c:1870
 l2cap_sock_create+0x118/0x1d0 net/bluetooth/l2cap_sock.c:1918
 bt_sock_create+0x155/0x220 net/bluetooth/af_bluetooth.c:130
 __sock_create+0x47b/0x900 net/socket.c:1495
 sock_create net/socket.c:1551 [inline]
 __sys_socket+0xe2/0x170 net/socket.c:1593
 __do_sys_socket net/socket.c:1602 [inline]
 __se_sys_socket net/socket.c:1600 [inline]
 __x64_sys_socket+0x76/0x80 net/socket.c:1600
 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

The buggy address belongs to the object at ffff88805f167000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1312 bytes inside of
 2048-byte region [ffff88805f167000, ffff88805f167800)
The buggy address belongs to the page:
page:ffffea00017c5800 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88805f160000 pfn:0x5f160
head:ffffea00017c5800 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea0000a13408 ffffea0000a5f608 ffff888016c42000
raw: ffff88805f160000 0000000000080004 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 0x1d28c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 5395, ts 216534919509, free_ts 216496108935
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1bbd/0x1ca0 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+0x80a/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 __kmalloc_node_track_caller+0x1fc/0x3a0 mm/slub.c:4963
 kmalloc_reserve net/core/skbuff.c:356 [inline]
 pskb_expand_head+0x127/0x10f0 net/core/skbuff.c:1710
 netlink_trim+0x180/0x220 net/netlink/af_netlink.c:1299
 netlink_broadcast_filtered+0x7c/0x1170 net/netlink/af_netlink.c:1511
 netlink_broadcast net/netlink/af_netlink.c:1556 [inline]
 nlmsg_multicast include/net/netlink.h:1044 [inline]
 nlmsg_notify+0xec/0x1a0 net/netlink/af_netlink.c:2550
 rtnl_notify net/core/rtnetlink.c:764 [inline]
 rtmsg_ifinfo_send net/core/rtnetlink.c:3913 [inline]
 rtmsg_ifinfo_event net/core/rtnetlink.c:3928 [inline]
 rtnetlink_event+0x13a/0x1a0 net/core/rtnetlink.c:5738
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:391
 call_netdevice_notifiers_extack net/core/dev.c:2074 [inline]
 call_netdevice_notifiers net/core/dev.c:2088 [inline]
 dev_set_mac_address+0x2e8/0x400 net/core/dev.c:9140
 dev_set_mac_address_user+0x2d/0x50 net/core/dev.c:9154
 do_setlink+0x8b0/0x3d60 net/core/rtnetlink.c:2739
 __rtnl_newlink net/core/rtnetlink.c:3455 [inline]
 rtnl_newlink+0x1658/0x1a50 net/core/rtnetlink.c:3577
 rtnetlink_rcv_msg+0x844/0xf30 net/core/rtnetlink.c:5687
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+0x1a5/0x200 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/0xd0 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+0x100/0x290 mm/slub.c:3238
 vm_area_alloc+0x20/0xe0 kernel/fork.c:350
 __mmap_region mm/mmap.c:1782 [inline]
 mmap_region+0xac0/0x1650 mm/mmap.c:2933
 do_mmap+0x819/0xe90 mm/mmap.c:1586
 vm_mmap_pgoff+0x1c1/0x2d0 mm/util.c:551
 ksys_mmap_pgoff+0x54b/0x790 mm/mmap.c:1635
 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:
 ffff88805f167400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805f167480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88805f167500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff88805f167580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805f167600: 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
2026/05/31 07:00 linux-5.15.y 241d66fa280c 6b4a8443 .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.