KASAN: slab-use-after-free Read in l2cap_sock_ready_cb

Status: upstream: reported on 2026/07/26 06:39
Reported-by: syzbot+2f58f221d0176ad8d867@syzkaller.appspotmail.com
First crash: 1d17h, last: 1d17h
▶ ▼ Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in l2cap_sock_ready_cb (2) prio:high bluetooth 19 syz error 124 7h16m 664d 0/29 upstream: reported syz repro on 2024/10/01 10:15
upstream KASAN: slab-use-after-free Read in l2cap_sock_ready_cb bluetooth 19 1 791d 787d 0/29 auto-obsoleted due to no activity on 2024/09/04 06:40
linux-5.15 KASAN: use-after-free Read in l2cap_sock_ready_cb (5) 19 1 69d 69d 0/3 upstream: reported on 2026/05/19 16:03
linux-5.15 KASAN: use-after-free Read in l2cap_sock_ready_cb (4) 19 1 180d 180d 0/3 auto-obsoleted due to no activity on 2026/05/08 02:22
linux-6.1 KASAN: use-after-free Read in l2cap_sock_ready_cb (2) 19 syz error 2 36d 141d 0/3 upstream: reported syz repro on 2026/03/08 14:59
linux-5.15 KASAN: use-after-free Read in l2cap_sock_ready_cb 19 2 582d 595d 0/3 auto-obsoleted due to no activity on 2025/04/01 01:17
linux-5.15 KASAN: use-after-free Read in l2cap_sock_ready_cb (2) 19 1 470d 470d 0/3 auto-obsoleted due to no activity on 2025/07/22 01:53
linux-6.1 KASAN: use-after-free Read in l2cap_sock_ready_cb 19 1 598d 598d 0/3 auto-obsoleted due to no activity on 2025/03/16 13:13
linux-5.15 KASAN: use-after-free Read in l2cap_sock_ready_cb (3) 19 1 284d 284d 0/3 auto-obsoleted due to no activity on 2026/01/24 11:53

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in l2cap_sock_ready_cb+0xd7/0x140 net/bluetooth/l2cap_sock.c:1744
Read of size 8 at addr ffff88805eaa94a8 by task kworker/u5:1/5087

CPU: 0 PID: 5087 Comm: kworker/u5:1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Workqueue: hci3 hci_rx_work
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
 l2cap_sock_ready_cb+0xd7/0x140 net/bluetooth/l2cap_sock.c:1744
 l2cap_chan_ready net/bluetooth/l2cap_core.c:1296 [inline]
 l2cap_le_start+0xaae/0x1350 net/bluetooth/l2cap_core.c:1408
 l2cap_conn_ready net/bluetooth/l2cap_core.c:1661 [inline]
 l2cap_connect_cfm+0x728/0x1160 net/bluetooth/l2cap_core.c:7493
 hci_connect_cfm+0x8f/0x130 include/net/bluetooth/hci_core.h:2004
 le_conn_complete_evt+0xf1d/0x1480 net/bluetooth/hci_event.c:5794
 hci_le_conn_complete_evt+0x187/0x440 net/bluetooth/hci_event.c:5820
 hci_event_func net/bluetooth/hci_event.c:7492 [inline]
 hci_event_packet+0x7b4/0x1280 net/bluetooth/hci_event.c:7547
 hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4017
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2811
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>

Allocated by task 12318:
 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+0xb7/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 sk_prot_alloc+0xe7/0x210 net/core/sock.c:2101
 sk_alloc+0x3a/0x350 net/core/sock.c:2157
 bt_sock_alloc+0x3b/0x330 net/bluetooth/af_bluetooth.c:148
 l2cap_sock_alloc net/bluetooth/l2cap_sock.c:1936 [inline]
 l2cap_sock_create+0x15a/0x2d0 net/bluetooth/l2cap_sock.c:1974
 bt_sock_create+0x159/0x230 net/bluetooth/af_bluetooth.c:132
 __sock_create+0x49e/0x940 net/socket.c:1571
 sock_create net/socket.c:1627 [inline]
 __sys_socket_create net/socket.c:1664 [inline]
 __sys_socket+0xd7/0x1b0 net/socket.c:1715
 __do_sys_socket net/socket.c:1729 [inline]
 __se_sys_socket net/socket.c:1727 [inline]
 __x64_sys_socket+0x7a/0x90 net/socket.c:1727
 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 12317:
 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
 sk_prot_free net/core/sock.c:2140 [inline]
 __sk_destruct+0x4e0/0x660 net/core/sock.c:2235
 l2cap_sock_release+0x16d/0x1e0 net/bluetooth/l2cap_sock.c:1448
 __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

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
 get_signal+0x11da/0x1390 kernel/signal.c:2679
 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

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 ffff88805eaa9000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1192 bytes inside of
 freed 2048-byte region [ffff88805eaa9000, ffff88805eaa9800)

The buggy address belongs to the physical page:
page:ffffea00017aaa00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5eaa8
head:ffffea00017aaa00 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 0000000080080008 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 5782, tgid 5782 (syz-executor), ts 80891092206, free_ts 26593189369
 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
 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 nbp_vlan_add+0x20f/0x3c0 net/bridge/br_vlan.c:1335
 nbp_vlan_init+0x376/0x460 net/bridge/br_vlan.c:1280
 br_add_if+0xacc/0xee0 net/bridge/br_if.c:680
 do_set_master net/core/rtnetlink.c:2718 [inline]
 do_setlink+0xcde/0x3f40 net/core/rtnetlink.c:2924
 __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
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
 free_contig_range+0xa1/0x150 mm/page_alloc.c:6421
 destroy_args+0x7d/0x840 mm/debug_vm_pgtable.c:1015
 debug_vm_pgtable+0x411/0x440 mm/debug_vm_pgtable.c:1400
 do_one_initcall+0x242/0x790 init/main.c:1249
 do_initcall_level+0x13d/0x1f0 init/main.c:1311
 do_initcalls+0x69/0xd0 init/main.c:1327
 kernel_init_freeable+0x3d9/0x560 init/main.c:1564
 kernel_init+0x1d/0x1c0 init/main.c:1454
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Memory state around the buggy address:
 ffff88805eaa9380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805eaa9400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88805eaa9480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88805eaa9500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805eaa9580: 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
2026/07/26 06:38 linux-6.6.y c5596480c50e 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in l2cap_sock_ready_cb
* Struck through repros no longer work on HEAD.