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

Status: upstream: reported on 2026/07/06 20:50
Reported-by: syzbot+5505c8db36dba9924cf3@syzkaller.appspotmail.com
First crash: 65d, last: 2d10h
▶ ▼ Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in bt_accept_unlink bluetooth 19 syz 250 9d01h 688d 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 19 1 342d 342d 0/2 auto-obsoleted due to no activity on 2026/01/11 02:55
linux-6.1 KASAN: use-after-free Read in bt_accept_unlink 19 1 456d 456d 0/3 auto-obsoleted due to no activity on 2025/09/18 23:51
linux-5.15 BUG: corrupted list in bt_accept_unlink 17 3 478d 519d 0/3 auto-obsoleted due to no activity on 2025/08/27 17:34
linux-5.15 KASAN: use-after-free Read in bt_accept_unlink 19 1 222d 222d 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 6d19h 256d 0/3 upstream: reported on 2025/12/27 18:50
linux-6.6 KASAN: slab-out-of-bounds Read in bt_accept_unlink 17 1 450d 450d 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 2016d 2012d 0/29 auto-closed as invalid on 2021/07/01 06:33
linux-5.15 KASAN: slab-out-of-bounds Read in bt_accept_unlink 17 1 337d 337d 0/3 auto-obsoleted due to no activity on 2026/01/15 10:51
linux-5.15 KASAN: use-after-free Read in bt_accept_unlink (2) 19 1 101d 101d 0/3 auto-obsoleted due to no activity on 2026/09/08 07:00

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in __lock_acquire+0x10c/0x7d80 kernel/locking/lockdep.c:5005
Read of size 8 at addr ffff88801f7ee540 by task syz-executor/8413

CPU: 1 PID: 8413 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 __lock_acquire+0x10c/0x7d80 kernel/locking/lockdep.c:5005
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
 _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:356 [inline]
 bt_accept_unlink+0x63/0x290 net/bluetooth/af_bluetooth.c:262
 l2cap_sock_teardown_cb+0x17e/0x450 net/bluetooth/l2cap_sock.c:1667
 l2cap_chan_del+0x92/0x5c0 net/bluetooth/l2cap_core.c:690
 l2cap_conn_del+0x342/0x630 net/bluetooth/l2cap_core.c:1810
 hci_disconn_cfm include/net/bluetooth/hci_core.h:2019 [inline]
 hci_conn_hash_flush+0xff/0x220 net/bluetooth/hci_conn.c:2571
 hci_dev_close_sync+0x9a1/0x1130 net/bluetooth/hci_sync.c:5401
 hci_dev_do_close net/bluetooth/hci_core.c:523 [inline]
 hci_unregister_dev+0x21a/0x500 net/bluetooth/hci_core.c:2709
 vhci_release+0x170/0x1c0 drivers/bluetooth/hci_vhci.c:701
 __fput+0x221/0x940 fs/file_table.c:418
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x986/0x2530 kernel/exit.c:890
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1032
 __do_sys_exit_group kernel/exit.c:1043 [inline]
 __se_sys_exit_group kernel/exit.c:1041 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1041
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fadbbb9e159
Code: Unable to access opcode bytes at 0x7fadbbb9e12f.
RSP: 002b:00007ffd96424878 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fadbbc344e6 RCX: 00007fadbbb9e159
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000016 R08: 0000000000000000 R09: 00007fadbbc34474
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd96425b30
R13: 00007fadbbc34474 R14: 000055556298d4e8 R15: 00007ffd96429ed0
 </TASK>

Allocated by task 5436:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc_node_track_caller+0xb4/0x230 mm/slab_common.c:1027
 kmalloc_reserve+0x116/0x240 net/core/skbuff.c:584
 pskb_expand_head+0x17a/0x1150 net/core/skbuff.c:2101
 netlink_trim+0x180/0x220 net/netlink/af_netlink.c:1301
 netlink_broadcast_filtered+0x6d/0x1130 net/netlink/af_netlink.c:1520
 netlink_broadcast net/netlink/af_netlink.c:1565 [inline]
 nlmsg_multicast include/net/netlink.h:1090 [inline]
 nlmsg_notify+0xe3/0x1a0 net/netlink/af_netlink.c:2593
 netdev_state_change+0xfe/0x170 net/core/dev.c:1423
 do_setlink+0x1010/0x3f40 net/core/rtnetlink.c:3159
 __rtnl_newlink net/core/rtnetlink.c:3715 [inline]
 rtnl_newlink+0x1848/0x2170 net/core/rtnetlink.c:3762
 rtnetlink_rcv_msg+0x843/0xf90 net/core/rtnetlink.c:6484
 netlink_rcv_skb+0x235/0x4c0 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x7b1/0x930 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x61b/0x980 net/socket.c:2595
 ___sys_sendmsg+0x2a6/0x360 net/socket.c:2649
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2687 [inline]
 __se_sys_sendmsg+0x1d0/0x2c0 net/socket.c:2685
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 5435:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3843
 skb_kfree_head net/core/skbuff.c:946 [inline]
 skb_free_head net/core/skbuff.c:958 [inline]
 skb_release_data+0x609/0x7f0 net/core/skbuff.c:988
 skb_release_all net/core/skbuff.c:1054 [inline]
 __kfree_skb net/core/skbuff.c:1068 [inline]
 consume_skb+0xb2/0x110 net/core/skbuff.c:1284
 netlink_recvmsg+0x5e7/0xe60 net/netlink/af_netlink.c:1977
 sock_recvmsg_nosec net/socket.c:1047 [inline]
 sock_recvmsg net/socket.c:1069 [inline]
 ____sys_recvmsg+0x2bd/0x5d0 net/socket.c:2814
 ___sys_recvmsg+0x214/0x590 net/socket.c:2856
 __sys_recvmsg net/socket.c:2886 [inline]
 __do_sys_recvmsg net/socket.c:2896 [inline]
 __se_sys_recvmsg net/socket.c:2893 [inline]
 __x64_sys_recvmsg+0x21e/0x2f0 net/socket.c:2893
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88801f7ee000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1344 bytes inside of
 freed 2048-byte region [ffff88801f7ee000, ffff88801f7ee800)

The buggy address belongs to the physical page:
page:ffffea00007dfa00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1f7e8
head:ffffea00007dfa00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017c42000 0000000000000000 dead000000000001
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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 5846, tgid 5846 (kworker/0:8), ts 92775859282, free_ts 92681259858
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
 prep_new_page mm/page_alloc.c:1589 [inline]
 get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
 alloc_slab_page+0x5d/0x180 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253
 __slab_alloc mm/slub.c:3339 [inline]
 __slab_alloc_node mm/slub.c:3392 [inline]
 slab_alloc_node mm/slub.c:3485 [inline]
 __kmem_cache_alloc_node+0x11f/0x250 mm/slub.c:3534
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc_node_track_caller+0xa4/0x230 mm/slab_common.c:1027
 kmalloc_reserve+0x116/0x240 net/core/skbuff.c:584
 __alloc_skb+0x138/0x2c0 net/core/skbuff.c:653
 alloc_skb include/linux/skbuff.h:1316 [inline]
 mld_newpack+0x14f/0xbf0 net/ipv6/mcast.c:1771
 add_grhead net/ipv6/mcast.c:1882 [inline]
 add_grec+0x1461/0x19c0 net/ipv6/mcast.c:2021
 mld_send_cr net/ipv6/mcast.c:2144 [inline]
 mld_ifc_work+0x6f1/0xd60 net/ipv6/mcast.c:2686
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 kthread+0x2fa/0x390 kernel/kthread.c:388
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 discard_slab mm/slub.c:2127 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2667
 put_cpu_partial+0x17c/0x250 mm/slub.c:2743
 __slab_free+0x319/0x400 mm/slub.c:3700
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:770
 slab_alloc_node mm/slub.c:3495 [inline]
 __kmem_cache_alloc_node+0x194/0x250 mm/slub.c:3534
 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
 kmalloc include/linux/slab.h:600 [inline]
 syslog_print+0x104/0x630 kernel/printk/printk.c:1553
 do_syslog+0x575/0x820 kernel/printk/printk.c:1732
 __do_sys_syslog kernel/printk/printk.c:1824 [inline]
 __se_sys_syslog kernel/printk/printk.c:1822 [inline]
 __x64_sys_syslog+0x7c/0x90 kernel/printk/printk.c:1822
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff88801f7ee400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801f7ee480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88801f7ee500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff88801f7ee580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801f7ee600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/07 18:01 linux-6.6.y 8b73de7da85f 680aa3e1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in bt_accept_unlink
2026/08/25 01:49 linux-6.6.y dc6160265ffc 614e416a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in bt_accept_unlink
2026/08/24 13:12 linux-6.6.y dc6160265ffc b55bd4c3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in bt_accept_unlink
2026/07/06 20:50 linux-6.6.y da47cbc25466 88b240e4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in bt_accept_unlink
* Struck through repros no longer work on HEAD.