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: 19d, last: 19d
▶ ▼ 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 209 2d16h 643d 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 296d 296d 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 410d 410d 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 432d 473d 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 176d 176d 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 24d 210d 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 404d 404d 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 1971d 1967d 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 292d 292d 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 56d 56d 0/3 upstream: reported on 2026/05/31 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 ffff8880782b2540 by task syz.0.5130/23667

CPU: 0 PID: 23667 Comm: syz.0.5130 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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:1649
 l2cap_chan_del+0xaf/0x5e0 net/bluetooth/l2cap_core.c:658
 l2cap_conn_del+0x38c/0x670 net/bluetooth/l2cap_core.c:1786
 hci_disconn_cfm include/net/bluetooth/hci_core.h:2014 [inline]
 hci_conn_hash_flush+0xff/0x220 net/bluetooth/hci_conn.c:2564
 hci_dev_close_sync+0x9a1/0x1130 net/bluetooth/hci_sync.c:5305
 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:691
 __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:884
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1026
 get_signal+0x12a6/0x1390 kernel/signal.c:2903
 arch_do_signal_or_restart+0xc2/0x7b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f6d50b5e68e
Code: Unable to access opcode bytes at 0x7f6d50b5e664.
RSP: 002b:00007f6d51a12f58 EFLAGS: 00000246 ORIG_RAX: 00000000000000e6
RAX: fffffffffffffdfc RBX: 00007f6d51a136c0 RCX: 00007f6d50b5e68e
RDX: 00007f6d51a12fb0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f6d50c33e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6d50e26128 R14: 00007f6d50e26090 R15: 00007ffc6422d338
 </TASK>

Allocated by task 32107:
 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
 __bpf_try_make_writable net/core/filter.c:1682 [inline]
 bpf_try_make_writable net/core/filter.c:1688 [inline]
 bpf_try_make_head_writable net/core/filter.c:1696 [inline]
 ____bpf_clone_redirect net/core/filter.c:2483 [inline]
 bpf_clone_redirect+0x1e6/0x4a0 net/core/filter.c:2452
 0xffffffffa00088b5
 bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
 __bpf_prog_run include/linux/filter.h:616 [inline]
 bpf_prog_run include/linux/filter.h:623 [inline]
 bpf_test_run+0x2df/0x870 net/bpf/test_run.c:424
 bpf_prog_test_run_skb+0xdbb/0x18f0 net/bpf/test_run.c:1089
 bpf_prog_test_run+0x31f/0x390 kernel/bpf/syscall.c:4132
 __sys_bpf+0x49d/0x890 kernel/bpf/syscall.c:5495
 __do_sys_bpf kernel/bpf/syscall.c:5581 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5579 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5579
 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 32107:
 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_add_bulk net/core/skbuff.c:1125 [inline]
 kfree_skb_list_reason+0x264/0x460 net/core/skbuff.c:1147
 __dev_xmit_skb net/core/dev.c:3950 [inline]
 __dev_queue_xmit+0x1f87/0x3630 net/core/dev.c:4416
 dev_queue_xmit include/linux/netdevice.h:3113 [inline]
 neigh_hh_output include/net/neighbour.h:527 [inline]
 neigh_output include/net/neighbour.h:541 [inline]
 ip_finish_output2+0xd4f/0x1260 net/ipv4/ip_output.c:235
 NF_HOOK_COND include/linux/netfilter.h:293 [inline]
 ip_output+0x2a5/0x3a0 net/ipv4/ip_output.c:436
 iptunnel_xmit+0x4d0/0x910 net/ipv4/ip_tunnel_core.c:82
 ip_tunnel_xmit+0x1d18/0x25b0 net/ipv4/ip_tunnel.c:844
 __gre_xmit net/ipv4/ip_gre.c:478 [inline]
 ipgre_xmit+0x7eb/0xb70 net/ipv4/ip_gre.c:674
 __netdev_start_xmit include/linux/netdevice.h:4943 [inline]
 netdev_start_xmit include/linux/netdevice.h:4957 [inline]
 xmit_one net/core/dev.c:3644 [inline]
 dev_hard_start_xmit+0x269/0x790 net/core/dev.c:3660
 __dev_queue_xmit+0x198c/0x3630 net/core/dev.c:4454
 dev_queue_xmit include/linux/netdevice.h:3113 [inline]
 __bpf_tx_skb+0x181/0x260 net/core/filter.c:2154
 ____bpf_clone_redirect net/core/filter.c:2489 [inline]
 bpf_clone_redirect+0x315/0x4a0 net/core/filter.c:2452
 0xffffffffa00088b5
 bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
 __bpf_prog_run include/linux/filter.h:616 [inline]
 bpf_prog_run include/linux/filter.h:623 [inline]
 bpf_test_run+0x2df/0x870 net/bpf/test_run.c:424
 bpf_prog_test_run_skb+0xdbb/0x18f0 net/bpf/test_run.c:1089
 bpf_prog_test_run+0x31f/0x390 kernel/bpf/syscall.c:4132
 __sys_bpf+0x49d/0x890 kernel/bpf/syscall.c:5495
 __do_sys_bpf kernel/bpf/syscall.c:5581 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5579 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5579
 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

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 __call_rcu_common kernel/rcu/tree.c:2721 [inline]
 call_rcu+0x153/0x900 kernel/rcu/tree.c:2837
 netlink_release+0x167e/0x1a70 net/netlink/af_netlink.c:801
 __sock_release net/socket.c:659 [inline]
 sock_close+0xa7/0x210 net/socket.c:1421
 __fput+0x221/0x940 fs/file_table.c:418
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Second to last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 __call_rcu_common kernel/rcu/tree.c:2721 [inline]
 call_rcu+0x153/0x900 kernel/rcu/tree.c:2837
 netlink_release+0x167e/0x1a70 net/netlink/af_netlink.c:801
 __sock_release net/socket.c:659 [inline]
 sock_close+0xa7/0x210 net/socket.c:1421
 __fput+0x221/0x940 fs/file_table.c:418
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff8880782b2000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1344 bytes inside of
 freed 2048-byte region [ffff8880782b2000, ffff8880782b2800)

The buggy address belongs to the physical page:
page:ffffea0001e0ac00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x782b0
head:ffffea0001e0ac00 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 14328, tgid 14318 (syz.2.2471), ts 452172064999, free_ts 447266597917
 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+0xa6/0x240 mm/slab_common.c:1014
 kmalloc_node include/linux/slab.h:620 [inline]
 kzalloc_node include/linux/slab.h:732 [inline]
 qdisc_alloc+0x95/0xa40 net/sched/sch_generic.c:951
 qdisc_create_dflt+0x63/0x430 net/sched/sch_generic.c:1012
 mq_init+0x2c7/0x660 net/sched/sch_mq.c:90
 qdisc_create_dflt+0x11e/0x430 net/sched/sch_generic.c:1019
 attach_default_qdiscs net/sched/sch_generic.c:1199 [inline]
 dev_activate+0x1e0/0x1160 net/sched/sch_generic.c:1253
 __dev_open+0x347/0x430 net/core/dev.c:1528
 __dev_change_flags+0x1e8/0x6a0 net/core/dev.c:8723
 dev_change_flags+0x7c/0x1a0 net/core/dev.c:8795
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
 napi_frag_unref include/linux/skbuff.h:3539 [inline]
 skb_release_data+0x3ca/0x7f0 net/core/skbuff.c:982
 skb_release_all net/core/skbuff.c:1054 [inline]
 __kfree_skb+0x57/0x70 net/core/skbuff.c:1068
 __tcp_close+0x216/0xdd0 net/ipv4/tcp.c:2822
 tcp_close+0x28/0x110 net/ipv4/tcp.c:2966
 tls_sk_proto_close+0x69e/0x930 net/tls/tls_main.c:396
 inet_release+0x13d/0x180 net/ipv4/af_inet.c:434
 __sock_release net/socket.c:659 [inline]
 sock_close+0xa7/0x210 net/socket.c:1421
 __fput+0x221/0x940 fs/file_table.c:418
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff8880782b2400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880782b2480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880782b2500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff8880782b2580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880782b2600: 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
2026/07/06 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.