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

Status: auto-obsoleted due to no activity on 2026/01/31 01:05
Reported-by: syzbot+e09c93587b38c46855e2@syzkaller.appspotmail.com
First crash: 347d, last: 276d
▶ ▼ 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 506d 631d 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 37d 163d 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 343d 429d 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 94d 240d 0/3 upstream: reported syz repro on 2025/11/27 04:46
linux-6.6 KASAN: slab-use-after-free Read in l2cap_sock_new_connection_cb 19 3 175d 201d 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 61d 61d 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 26d 642d 0/29 upstream: reported syz repro on 2024/10/21 08:46

Sample crash report:
 </TASK>
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+0x1f5/0x2a0 net/bluetooth/l2cap_sock.c:1517
Read of size 8 at addr ffff888027975540 by task kworker/u5:2/4271

CPU: 0 PID: 4271 Comm: kworker/u5:2 Not tainted 6.1.147-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: hci3 hci_rx_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x200 mm/kasan/report.c:418
 kasan_report+0x10b/0x140 mm/kasan/report.c:522
 l2cap_sock_new_connection_cb+0x1f5/0x2a0 net/bluetooth/l2cap_sock.c:1517
 l2cap_connect_cfm+0x35d/0x10d0 net/bluetooth/l2cap_core.c:8348
 hci_connect_cfm+0x8f/0x130 include/net/bluetooth/hci_core.h:1787
 le_conn_complete_evt+0xdb2/0x1320 net/bluetooth/hci_event.c:5835
 hci_le_conn_complete_evt+0x183/0x440 net/bluetooth/hci_event.c:5861
 hci_event_func net/bluetooth/hci_event.c:7342 [inline]
 hci_event_packet+0x791/0x1210 net/bluetooth/hci_event.c:7397
 hci_rx_work+0x3eb/0xd40 net/bluetooth/hci_core.c:4083
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 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 4271:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:383
 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:2050
 sk_alloc+0x36/0x340 net/core/sock.c:2103
 bt_sock_alloc+0x36/0x130 net/bluetooth/af_bluetooth.c:148
 l2cap_sock_alloc net/bluetooth/l2cap_sock.c:1914 [inline]
 l2cap_sock_new_connection_cb+0xde/0x2a0 net/bluetooth/l2cap_sock.c:1502
 l2cap_connect_cfm+0x35d/0x10d0 net/bluetooth/l2cap_core.c:8348
 hci_connect_cfm+0x8f/0x130 include/net/bluetooth/hci_core.h:1787
 le_conn_complete_evt+0xdb2/0x1320 net/bluetooth/hci_event.c:5835
 hci_le_conn_complete_evt+0x183/0x440 net/bluetooth/hci_event.c:5861
 hci_event_func net/bluetooth/hci_event.c:7342 [inline]
 hci_event_packet+0x791/0x1210 net/bluetooth/hci_event.c:7397
 hci_rx_work+0x3eb/0xd40 net/bluetooth/hci_core.c:4083
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 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 5071:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2d/0x50 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1724 [inline]
 slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1750
 slab_free mm/slub.c:3661 [inline]
 __kmem_cache_free+0xb6/0x1f0 mm/slub.c:3674
 sk_prot_free net/core/sock.c:2086 [inline]
 __sk_destruct+0x49c/0x630 net/core/sock.c:2172
 l2cap_sock_cleanup_listen+0xda/0x270 net/bluetooth/l2cap_sock.c:1482
 l2cap_sock_release+0x59/0x1c0 net/bluetooth/l2cap_sock.c:1445
 __sock_release net/socket.c:654 [inline]
 sock_close+0xd5/0x240 net/socket.c:1400
 __fput+0x22c/0x920 fs/file_table.c:320
 task_work_run+0x1ca/0x250 kernel/task_work.c:203
 get_signal+0x11a6/0x1350 kernel/signal.c:2648
 arch_do_signal_or_restart+0xb0/0x1230 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xb1/0x140 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:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888027975000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1344 bytes inside of
 2048-byte region [ffff888027975000, ffff888027975800)

The buggy address belongs to the physical page:
page:ffffea00009e5c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27970
head:ffffea00009e5c00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888017442000
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 0xd2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4276, tgid 4276 (syz-executor), ts 80372652330, free_ts 80198447373
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2532
 prep_new_page mm/page_alloc.c:2539 [inline]
 get_page_from_freelist+0x1a26/0x1ac0 mm/page_alloc.c:4328
 __alloc_pages+0x1df/0x4e0 mm/page_alloc.c:5614
 alloc_slab_page+0x5d/0x160 mm/slub.c:1794
 allocate_slab mm/slub.c:1939 [inline]
 new_slab+0x87/0x2c0 mm/slub.c:1992
 ___slab_alloc+0xbc6/0x1220 mm/slub.c:3180
 __slab_alloc mm/slub.c:3279 [inline]
 slab_alloc_node mm/slub.c:3364 [inline]
 __kmem_cache_alloc_node+0x1a0/0x260 mm/slub.c:3437
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc_node_track_caller+0x9e/0x230 mm/slab_common.c:956
 kmalloc_reserve net/core/skbuff.c:446 [inline]
 __alloc_skb+0x22a/0x7e0 net/core/skbuff.c:515
 alloc_skb include/linux/skbuff.h:1271 [inline]
 nlmsg_new include/net/netlink.h:991 [inline]
 inet6_ifinfo_notify+0x6c/0x110 net/ipv6/addrconf.c:6109
 addrconf_notify+0xc4c/0xf40 net/ipv6/addrconf.c:3706
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
 netdev_state_change+0xd2/0x140 net/core/dev.c:1390
 __hsr_set_operstate net/hsr/hsr_device.c:37 [inline]
 hsr_set_operstate net/hsr/hsr_device.c:-1 [inline]
 hsr_check_carrier_and_operstate+0x54c/0x6b0 net/hsr/hsr_device.c:102
 hsr_netdev_notify+0x37d/0xaf0 net/hsr/hsr_main.c:60
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3384
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3479
 free_slab mm/slub.c:2031 [inline]
 discard_slab mm/slub.c:2037 [inline]
 __unfreeze_partials+0x1a5/0x200 mm/slub.c:2586
 put_cpu_partial+0x17c/0x250 mm/slub.c:2662
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x480 mm/slab.h:737
 slab_alloc_node mm/slub.c:3398 [inline]
 __kmem_cache_alloc_node+0x140/0x260 mm/slub.c:3437
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc+0xa0/0x240 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 fib6_info_alloc+0x2e/0xe0 net/ipv6/ip6_fib.c:156
 ip6_route_info_create+0x44f/0x1210 net/ipv6/route.c:3794
 ip6_route_add+0x24/0x130 net/ipv6/route.c:3890
 addrconf_add_mroute net/ipv6/addrconf.c:2507 [inline]
 addrconf_add_dev+0x253/0x330 net/ipv6/addrconf.c:2525
 addrconf_dev_config net/ipv6/addrconf.c:3425 [inline]
 addrconf_init_auto_addrs+0x601/0xa60 net/ipv6/addrconf.c:3513
 addrconf_notify+0xaca/0xf40 net/ipv6/addrconf.c:3686

Memory state around the buggy address:
 ffff888027975400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888027975480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888027975500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff888027975580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888027975600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/12 10:31 linux-6.1.y 3594f306da12 c06e8995 .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
2025/10/23 01:04 linux-6.1.y 8e6e2188d949 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_sock_new_connection_cb
2025/10/06 18:56 linux-6.1.y 882efbdd9d34 91305dbe .config console log report info ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_sock_new_connection_cb
2025/08/15 10:13 linux-6.1.y 3594f306da12 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_sock_new_connection_cb
* Struck through repros no longer work on HEAD.