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

Status: fixed on 2026/08/18 00:55
Subsystems: kernel
Labels: prio:high actionable
[Documentation on labels]
Reported-by: syzbot+fed5dce4553262f3b35c@syzkaller.appspotmail.com
Fix commit: bb067a99a035 Bluetooth: bnep: pin L2CAP connection during netdev registration
First crash: 126d, last: 104d
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
2502f3e1 moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Read in netdev_register_kobject (2) 2026/06/01 14:10 2026/06/01 14:10 2026/06/01 15:07 386cc6da
c54ba430 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ✅ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in netdev_register_kobject (2) 2026/06/01 14:09 2026/06/01 14:09 2026/06/01 15:02 386cc6da
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH] Bluetooth: bnep: pin L2CAP connection during netdev registration 2 (2) 2026/06/30 20:32
[syzbot] [kernel?] KASAN: slab-use-after-free Read in netdev_register_kobject (2) 0 (1) 2026/06/01 15:08
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in netdev_register_kobject kernel 19 1 476d 476d 0/29 closed as invalid on 2025/07/02 15:51
upstream general protection fault in netdev_register_kobject kernel 8 syz, C done 512 1080d 1114d 0/29 closed as dup on 2023/08/31 14:15
linux-4.19 general protection fault in netdev_register_kobject 2 1 1729d 1729d 0/1 auto-closed as invalid on 2022/04/23 17:30

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in kobject_get+0x136/0x150 lib/kobject.c:639
Read of size 1 at addr ffff88806195cd1c by task syz.0.1153/10834

CPU: 2 UID: 0 PID: 10834 Comm: syz.0.1153 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1d0 mm/kasan/report.c:595
 kobject_get+0x136/0x150 lib/kobject.c:639
 get_device drivers/base/core.c:3802 [inline]
 device_add+0x19f/0x1950 drivers/base/core.c:3614
 netdev_register_kobject+0x1a9/0x3d0 net/core/net-sysfs.c:2343
 register_netdevice+0x151c/0x24b0 net/core/dev.c:11423
 register_netdev+0x34/0x50 net/core/dev.c:11539
 bnep_add_connection+0x723/0xd30 net/bluetooth/bnep/core.c:646
 do_bnep_sock_ioctl.isra.0+0x3ac/0x5b0 net/bluetooth/bnep/sock.c:83
 sock_do_ioctl+0x118/0x280 net/socket.c:1313
 sock_ioctl+0x599/0x6b0 net/socket.c:1434
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1812d9ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1813bc8028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f1813015fa0 RCX: 00007f1812d9ce59
RDX: 00002000000000c0 RSI: 00000000400442c8 RDI: 0000000000000005
RBP: 00007f1812e32d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1813016038 R14: 00007f1813015fa0 R15: 00007fff0c06a388
 </TASK>

Allocated by task 5750:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 __hci_conn_add+0x1f4/0x1da0 net/bluetooth/hci_conn.c:1032
 hci_conn_add_unset+0x76/0x120 net/bluetooth/hci_conn.c:1159
 hci_conn_request_evt+0xa58/0xbb0 net/bluetooth/hci_event.c:3333
 hci_event_func net/bluetooth/hci_event.c:7796 [inline]
 hci_event_packet+0x8e9/0xcd0 net/bluetooth/hci_event.c:7847
 hci_rx_work+0x451/0xfc0 net/bluetooth/hci_core.c:4040
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314
 process_scheduled_works kernel/workqueue.c:3397 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 10685:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2689 [inline]
 slab_free mm/slub.c:6251 [inline]
 kfree+0x223/0x6c0 mm/slub.c:6566
 device_release+0xd2/0x270 drivers/base/core.c:2566
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1f7/0x640 lib/kobject.c:737
 put_device drivers/base/core.c:3814 [inline]
 device_unregister+0x2f/0xe0 drivers/base/core.c:3937
 hci_conn_del_sysfs+0xb9/0x1a0 net/bluetooth/hci_sysfs.c:79
 hci_conn_cleanup net/bluetooth/hci_conn.c:173 [inline]
 hci_conn_del+0x506/0x1180 net/bluetooth/hci_conn.c:1309
 hci_conn_hash_flush+0x186/0x280 net/bluetooth/hci_conn.c:2737
 hci_dev_close_sync+0x5cf/0x13c0 net/bluetooth/hci_sync.c:5383
 hci_dev_do_close+0x2e/0xb0 net/bluetooth/hci_core.c:502
 hci_unregister_dev+0x227/0x670 net/bluetooth/hci_core.c:2679
 vhci_release+0x17d/0x230 drivers/bluetooth/hci_vhci.c:690
 __fput+0x3ff/0xb50 fs/file_table.c:510
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x951/0x2af0 kernel/exit.c:976
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1119
 __do_sys_exit_group kernel/exit.c:1130 [inline]
 __se_sys_exit_group kernel/exit.c:1128 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1128
 x64_sys_call+0x102c/0x1530 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Last potentially related work creation:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:556
 insert_work+0x36/0x230 kernel/workqueue.c:2226
 __queue_work+0x9a2/0x1270 kernel/workqueue.c:2393
 __queue_delayed_work+0x357/0x450 kernel/workqueue.c:2560
 queue_delayed_work_on+0x180/0x1e0 kernel/workqueue.c:2612
 queue_delayed_work include/linux/workqueue.h:713 [inline]
 hci_conn_drop include/net/bluetooth/hci_core.h:1712 [inline]
 hci_conn_drop include/net/bluetooth/hci_core.h:1686 [inline]
 l2cap_chan_del+0x649/0x930 net/bluetooth/l2cap_core.c:674
 l2cap_conn_del+0x395/0x710 net/bluetooth/l2cap_core.c:1804
 l2cap_disconn_cfm net/bluetooth/l2cap_core.c:7511 [inline]
 l2cap_disconn_cfm+0x9f/0x100 net/bluetooth/l2cap_core.c:7504
 hci_disconn_cfm include/net/bluetooth/hci_core.h:2154 [inline]
 hci_conn_hash_flush+0x10e/0x280 net/bluetooth/hci_conn.c:2736
 hci_dev_close_sync+0x5cf/0x13c0 net/bluetooth/hci_sync.c:5383
 hci_dev_do_close+0x2e/0xb0 net/bluetooth/hci_core.c:502
 hci_unregister_dev+0x227/0x670 net/bluetooth/hci_core.c:2679
 vhci_release+0x17d/0x230 drivers/bluetooth/hci_vhci.c:690
 __fput+0x3ff/0xb50 fs/file_table.c:510
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x951/0x2af0 kernel/exit.c:976
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1119
 __do_sys_exit_group kernel/exit.c:1130 [inline]
 __se_sys_exit_group kernel/exit.c:1128 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1128
 x64_sys_call+0x102c/0x1530 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88806195c000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 3356 bytes inside of
 freed 8192-byte region [ffff88806195c000, ffff88806195e000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x61958
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b843180 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b843180 dead000000000100 dead000000000122
head: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
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 7332, tgid 7332 (syz-executor), ts 89209836633, free_ts 89188109028
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1853
 prep_new_page mm/page_alloc.c:1861 [inline]
 get_page_from_freelist+0x11a6/0x3410 mm/page_alloc.c:3941
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5221
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab mm/slub.c:3467 [inline]
 new_slab+0xa6/0x6c0 mm/slub.c:3525
 refill_objects+0x277/0x420 mm/slub.c:7272
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x375/0x650 mm/slub.c:4652
 alloc_from_pcs mm/slub.c:4750 [inline]
 slab_alloc_node mm/slub.c:4884 [inline]
 __kmalloc_cache_noprof+0x493/0x6f0 mm/slub.c:5415
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 macvlan_port_create drivers/net/macvlan.c:1260 [inline]
 macvlan_common_newlink+0x476/0x18b0 drivers/net/macvlan.c:1498
 rtnl_newlink_create net/core/rtnetlink.c:3864 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3995 [inline]
 rtnl_newlink+0x1499/0x2380 net/core/rtnetlink.c:4110
 rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6997
 netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2555
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 __sys_sendto+0x468/0x4b0 net/socket.c:2265
 __do_sys_sendto net/socket.c:2272 [inline]
 __se_sys_sendto net/socket.c:2268 [inline]
 __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2268
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
page last free pid 7332 tgid 7332 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1397 [inline]
 __free_frozen_pages+0x794/0x10a0 mm/page_alloc.c:2938
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xf0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4570 [inline]
 slab_alloc_node mm/slub.c:4899 [inline]
 __kmalloc_cache_noprof+0x243/0x6f0 mm/slub.c:5415
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 garp_init_port net/802/garp.c:550 [inline]
 garp_init_applicant+0x38d/0x4e0 net/802/garp.c:578
 register_vlan_dev+0x197/0x910 net/8021q/vlan.c:167
 vlan_newlink+0x48c/0x750 net/8021q/vlan_netlink.c:194
 rtnl_newlink_create net/core/rtnetlink.c:3864 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3995 [inline]
 rtnl_newlink+0x1499/0x2380 net/core/rtnetlink.c:4110
 rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6997
 netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2555
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 __sys_sendto+0x468/0x4b0 net/socket.c:2265
 __do_sys_sendto net/socket.c:2272 [inline]
 __se_sys_sendto net/socket.c:2268 [inline]
 __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2268
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94

Memory state around the buggy address:
 ffff88806195cc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88806195cc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88806195cd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88806195cd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88806195ce00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/06 10:26 upstream c10130c234c8 cc095639 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in netdev_register_kobject
2026/05/24 04:18 upstream 4cbfe4502e3d c69befb3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in netdev_register_kobject
2026/05/15 06:34 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 5cbb61bf4168 6ccb967e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 KASAN: slab-use-after-free Read in netdev_register_kobject
* Struck through repros no longer work on HEAD.