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KASAN: use-after-free Read in l2cap_sock_new_connection_cb (3)

Status: upstream: reported on 2026/02/12 04:37
Reported-by: syzbot+60ce389fe08a19dff2b9@syzkaller.appspotmail.com
First crash: 3d14h, last: 3d14h
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: use-after-free Read in l2cap_sock_new_connection_cb 19 7 346d 471d 0/3 auto-obsoleted due to no activity on 2025/06/14 04:52
linux-5.15 KASAN: use-after-free Read in l2cap_sock_new_connection_cb 19 3 183d 269d 0/3 auto-obsoleted due to no activity on 2025/11/24 17:00
linux-5.15 KASAN: use-after-free Read in l2cap_sock_new_connection_cb (2) origin:lts-only 19 syz inconclusive 2 25d 80d 0/3 upstream: reported syz repro on 2025/11/27 04:46
linux-6.1 KASAN: use-after-free Read in l2cap_sock_new_connection_cb (2) 19 4 115d 187d 0/3 auto-obsoleted due to no activity on 2026/01/31 01:05
linux-6.6 KASAN: slab-use-after-free Read in l2cap_sock_new_connection_cb 19 3 14d 41d 0/2 upstream: reported on 2026/01/05 08:24
upstream KASAN: slab-use-after-free Read in l2cap_sock_new_connection_cb bluetooth 19 syz error 120 13h54m 482d 0/29 upstream: reported syz repro on 2024/10/21 08:46

Sample crash report:
 </TASK>
kobject_add_internal failed for hci2:201 with -EEXIST, don't try to register things with the same name in the same directory.
Bluetooth: hci2: failed to register connection device
==================================================================
BUG: KASAN: use-after-free in l2cap_sock_new_connection_cb+0x1f5/0x2a0 net/bluetooth/l2cap_sock.c:1520
Read of size 8 at addr ffff88801f2ca548 by task kworker/u5:4/4280

CPU: 0 PID: 4280 Comm: kworker/u5:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Workqueue: hci2 hci_rx_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 l2cap_sock_new_connection_cb+0x1f5/0x2a0 net/bluetooth/l2cap_sock.c:1520
 l2cap_connect_cfm+0x35f/0x1120 net/bluetooth/l2cap_core.c:8349
 hci_connect_cfm+0x8f/0x130 include/net/bluetooth/hci_core.h:1814
 le_conn_complete_evt+0x10ec/0x1670 net/bluetooth/hci_event.c:5882
 hci_le_conn_complete_evt+0x183/0x440 net/bluetooth/hci_event.c:5908
 hci_event_func net/bluetooth/hci_event.c:7412 [inline]
 hci_event_packet+0x7b6/0x1280 net/bluetooth/hci_event.c:7467
 hci_rx_work+0x3eb/0xd40 net/bluetooth/hci_core.c:4083
 process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

Allocated by task 4280:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 __do_kmalloc_node mm/slab_common.c:936 [inline]
 __kmalloc+0xb0/0x240 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 sk_prot_alloc+0xe7/0x210 net/core/sock.c:2052
 sk_alloc+0x36/0x340 net/core/sock.c:2108
 bt_sock_alloc+0x36/0x130 net/bluetooth/af_bluetooth.c:148
 l2cap_sock_alloc net/bluetooth/l2cap_sock.c:1917 [inline]
 l2cap_sock_new_connection_cb+0xde/0x2a0 net/bluetooth/l2cap_sock.c:1505
 l2cap_connect_cfm+0x35f/0x1120 net/bluetooth/l2cap_core.c:8349
 hci_connect_cfm+0x8f/0x130 include/net/bluetooth/hci_core.h:1814
 le_conn_complete_evt+0x10ec/0x1670 net/bluetooth/hci_event.c:5882
 hci_le_conn_complete_evt+0x183/0x440 net/bluetooth/hci_event.c:5908
 hci_event_func net/bluetooth/hci_event.c:7412 [inline]
 hci_event_packet+0x7b6/0x1280 net/bluetooth/hci_event.c:7467
 hci_rx_work+0x3eb/0xd40 net/bluetooth/hci_core.c:4083
 process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Freed by task 9094:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x2d/0x50 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 __kmem_cache_free+0xb6/0x1f0 mm/slub.c:3700
 sk_prot_free net/core/sock.c:2091 [inline]
 __sk_destruct+0x4ba/0x650 net/core/sock.c:2177
 l2cap_sock_cleanup_listen+0xda/0x270 net/bluetooth/l2cap_sock.c:1485
 l2cap_sock_release+0x66/0x1e0 net/bluetooth/l2cap_sock.c:1446
 __sock_release net/socket.c:654 [inline]
 sock_close+0xd5/0x240 net/socket.c:1399
 __fput+0x22c/0x920 fs/file_table.c:320
 task_work_run+0x1d0/0x260 kernel/task_work.c:203
 get_signal+0x11a6/0x1350 kernel/signal.c:2648
 arch_do_signal_or_restart+0xc4/0x1350 arch/x86/kernel/signal.c:871
 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:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xb2/0xc0 mm/kasan/generic.c:486
 call_rcu+0x14f/0x990 kernel/rcu/tree.c:2849
 netdev_for_each_tx_queue include/linux/netdevice.h:2465 [inline]
 dev_shutdown+0x92/0x440 net/sched/sch_generic.c:1492
 unregister_netdevice_many+0xa4f/0x1930 net/core/dev.c:10994
 default_device_exit_batch+0x9e6/0xa80 net/core/dev.c:11516
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x791/0xba0 net/core/net_namespace.c:640
 process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Second to last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xb2/0xc0 mm/kasan/generic.c:486
 call_rcu+0x14f/0x990 kernel/rcu/tree.c:2849
 netlink_release+0x158e/0x19e0 net/netlink/af_netlink.c:799
 __sock_release net/socket.c:654 [inline]
 sock_release+0x7b/0x140 net/socket.c:682
 rtnetlink_net_exit+0x3c/0x60 net/core/rtnetlink.c:6235
 ops_exit_list net/core/net_namespace.c:172 [inline]
 cleanup_net+0x706/0xba0 net/core/net_namespace.c:640
 process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff88801f2ca000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1352 bytes inside of
 2048-byte region [ffff88801f2ca000, ffff88801f2ca800)

The buggy address belongs to the physical page:
page:ffffea00007cb200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1f2c8
head:ffffea00007cb200 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000001 ffff888017442000
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 1, tgid 1 (swapper/0), ts 3806590500, free_ts 0
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2559
 prep_new_page mm/page_alloc.c:2566 [inline]
 get_page_from_freelist+0x1a1e/0x1ab0 mm/page_alloc.c:4357
 __alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5643
 alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2115
 alloc_slab_page+0x5d/0x160 mm/slub.c:1799
 allocate_slab mm/slub.c:1944 [inline]
 new_slab+0x87/0x2c0 mm/slub.c:1997
 ___slab_alloc+0xbc6/0x1240 mm/slub.c:3154
 __slab_alloc mm/slub.c:3240 [inline]
 slab_alloc_node mm/slub.c:3325 [inline]
 __kmem_cache_alloc_node+0x1a0/0x260 mm/slub.c:3398
 kmalloc_trace+0x26/0xe0 mm/slab_common.c:1026
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 acpi_os_allocate_zeroed include/acpi/platform/aclinuxex.h:57 [inline]
 acpi_ds_create_walk_state+0xe2/0x270 drivers/acpi/acpica/dswstate.c:518
 acpi_ps_execute_method+0x21c/0x7b0 drivers/acpi/acpica/psxface.c:134
 acpi_ns_evaluate+0x617/0x9d0 drivers/acpi/acpica/nseval.c:205
 acpi_ut_evaluate_object+0x12f/0x490 drivers/acpi/acpica/uteval.c:60
 acpi_ut_execute_STA+0x44/0x130 drivers/acpi/acpica/uteval.c:223
 acpi_ns_get_device_callback+0x210/0x4b0 drivers/acpi/acpica/nsxfeval.c:723
 acpi_ns_walk_namespace+0x235/0x680 drivers/acpi/acpica/nswalk.c:-1
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88801f2ca400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801f2ca480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88801f2ca500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff88801f2ca580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801f2ca600: 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
2026/02/12 04:37 linux-6.1.y 8ce36b2849ef 76a109e2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_sock_new_connection_cb
* Struck through repros no longer work on HEAD.