KASAN: use-after-free Read in l2cap_sock_new_connection_cb (2)

Status: auto-obsoleted due to no activity on 2026/07/31 05:17
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+424eb096397600e92a91@syzkaller.appspotmail.com
First crash: 248d, last: 102d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/12/01 linux-5.15.y (ToT) cc5ec8769306 syz [report] KASAN: use-after-free Write in __l2cap_chan_add
2025/11/30 upstream (ToT) e69c7c175115 syz Didn't crash
▶ ▼ Similar bugs (7)
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 514d 639d 0/3 auto-obsoleted due to no activity on 2025/06/14 04:52
linux-6.1 KASAN: use-after-free Read in l2cap_sock_new_connection_cb (3) 19 10 46d 171d 0/3 upstream: reported on 2026/02/12 04:37
linux-5.15 KASAN: use-after-free Read in l2cap_sock_new_connection_cb 19 3 351d 437d 0/3 auto-obsoleted due to no activity on 2025/11/24 17:00
linux-6.1 KASAN: use-after-free Read in l2cap_sock_new_connection_cb (2) 19 4 284d 355d 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 183d 209d 0/2 auto-obsoleted due to no activity on 2026/05/11 21:45
linux-6.6 KASAN: slab-use-after-free Read in l2cap_sock_new_connection_cb (2) 19 1 69d 69d 0/2 upstream: reported on 2026/05/25 08:37
upstream KASAN: slab-use-after-free Read in l2cap_sock_new_connection_cb prio:high bluetooth 19 syz error 203 35d 650d 0/29 upstream: reported syz repro on 2024/10/21 08:46
▶ ▼ Last patch testing requests (3)
Created Duration User Patch Repo Result
2026/07/21 08:55 18m retest repro linux-5.15.y OK log
2026/04/22 04:55 21m retest repro linux-5.15.y report log
2026/02/09 03:06 15m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2025/12/22 21:00 2h14m fix candidate upstream OK (0) job log

Sample crash report:
kobject_add_internal failed for hci3:201 with -EEXIST, don't try to register things with the same name in the same directory.
Bluetooth: hci3: failed to register connection device
==================================================================
BUG: KASAN: use-after-free in l2cap_sock_new_connection_cb+0x125/0x1c0 net/bluetooth/l2cap_sock.c:1494
Read of size 8 at addr ffff888062cda550 by task kworker/u5:0/146

CPU: 0 PID: 146 Comm: kworker/u5:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: hci3 hci_rx_work
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
 l2cap_sock_new_connection_cb+0x125/0x1c0 net/bluetooth/l2cap_sock.c:1494
 l2cap_connect_cfm+0x35d/0x10f0 net/bluetooth/l2cap_core.c:8304
 hci_connect_cfm include/net/bluetooth/hci_core.h:1505 [inline]
 le_conn_complete_evt+0xd42/0x15c0 net/bluetooth/hci_event.c:5456
 hci_le_conn_complete_evt net/bluetooth/hci_event.c:5481 [inline]
 hci_le_meta_evt+0x285/0x3c90 net/bluetooth/hci_event.c:6203
 hci_event_packet+0xe48/0x1370 net/bluetooth/hci_event.c:6552
 hci_rx_work+0x255/0xa10 net/bluetooth/hci_core.c:5160
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Allocated by task 146:
 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:1867
 l2cap_sock_new_connection_cb+0xd1/0x1c0 net/bluetooth/l2cap_sock.c:1479
 l2cap_connect_cfm+0x35d/0x10f0 net/bluetooth/l2cap_core.c:8304
 hci_connect_cfm include/net/bluetooth/hci_core.h:1505 [inline]
 le_conn_complete_evt+0xd42/0x15c0 net/bluetooth/hci_event.c:5456
 hci_le_conn_complete_evt net/bluetooth/hci_event.c:5481 [inline]
 hci_le_meta_evt+0x285/0x3c90 net/bluetooth/hci_event.c:6203
 hci_event_packet+0xe48/0x1370 net/bluetooth/hci_event.c:6552
 hci_rx_work+0x255/0xa10 net/bluetooth/hci_core.c:5160
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Freed by task 5333:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xea/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kfree+0xef/0x2a0 mm/slub.c:4564
 sk_prot_free net/core/sock.c:1905 [inline]
 __sk_destruct+0x578/0x840 net/core/sock.c:1991
 l2cap_sock_cleanup_listen+0xda/0x270 net/bluetooth/l2cap_sock.c:1459
 l2cap_sock_release+0x66/0x1e0 net/bluetooth/l2cap_sock.c:1420
 __sock_release net/socket.c:651 [inline]
 sock_close+0xd5/0x240 net/socket.c:1345
 __fput+0x234/0x930 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 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

Last potentially related work creation:
 kasan_save_stack+0x35/0x60 mm/kasan/common.c:38
 kasan_record_aux_stack+0xb8/0x100 mm/kasan/generic.c:348
 kvfree_call_rcu+0x105/0x7d0 kernel/rcu/tree.c:3600
 drop_sysctl_table+0x359/0x4e0 fs/proc/proc_sysctl.c:1685
 unregister_sysctl_table+0x87/0x130 fs/proc/proc_sysctl.c:1723
 __devinet_sysctl_unregister net/ipv4/devinet.c:2626 [inline]
 devinet_sysctl_unregister net/ipv4/devinet.c:2654 [inline]
 inetdev_destroy net/ipv4/devinet.c:326 [inline]
 inetdev_event+0x6da/0x1370 net/ipv4/devinet.c:1611
 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:2061 [inline]
 call_netdevice_notifiers net/core/dev.c:2075 [inline]
 unregister_netdevice_many+0x1049/0x19f0 net/core/dev.c:11134
 ip6gre_exit_batch_net+0x44d/0x4a0 net/ipv6/ip6_gre.c:1657
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x791/0xba0 net/core/net_namespace.c:635
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

The buggy address belongs to the object at ffff888062cda000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1360 bytes inside of
 2048-byte region [ffff888062cda000, ffff888062cda800)
The buggy address belongs to the page:
page:ffffea00018b3600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x62cd8
head:ffffea00018b3600 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea00008cd400 0000000300000003 ffff888016c42000
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 4185, ts 68127152765, free_ts 22808732397
 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:5487
 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]
 slab_alloc mm/slub.c:3233 [inline]
 __kmalloc+0x1cd/0x330 mm/slub.c:4408
 kmalloc include/linux/slab.h:612 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 ops_init+0x8b/0x600 net/core/net_namespace.c:128
 setup_net+0x39e/0xa10 net/core/net_namespace.c:333
 copy_net_ns+0x348/0x5b0 net/core/net_namespace.c:503
 create_new_namespaces+0x3d3/0x6f0 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x116/0x160 kernel/nsproxy.c:226
 ksys_unshare+0x4ca/0x8b0 kernel/fork.c:3175
 __do_sys_unshare kernel/fork.c:3249 [inline]
 __se_sys_unshare kernel/fork.c:3247 [inline]
 __x64_sys_unshare+0x34/0x40 kernel/fork.c:3247
 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
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_contig_range+0x96/0xf0 mm/page_alloc.c:9406
 destroy_args+0xf0/0xa00 mm/debug_vm_pgtable.c:1018
 debug_vm_pgtable+0x321/0x380 mm/debug_vm_pgtable.c:1336
 do_one_initcall+0x272/0x730 init/main.c:1316
 do_initcall_level+0x137/0x1f0 init/main.c:1389
 do_initcalls+0x4b/0x90 init/main.c:1405
 kernel_init_freeable+0x3e9/0x570 init/main.c:1629
 kernel_init+0x19/0x1b0 init/main.c:1520
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Memory state around the buggy address:
 ffff888062cda400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888062cda480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888062cda500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff888062cda580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888062cda600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/21 11:56 linux-5.15.y 9eec9a14ee10 6f1aa2f9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_sock_new_connection_cb
2025/11/27 04:45 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_sock_new_connection_cb
* Struck through repros no longer work on HEAD.