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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: 41d, last: 8d09h
▶ ▼ 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 384d 508d 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 220d 306d 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 62d 118d 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 153d 225d 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 52d 79d 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 146 6d20h 520d 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:1527
Read of size 8 at addr ffff888060f13548 by task kworker/u5:1/3456

CPU: 1 PID: 3456 Comm: kworker/u5:1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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:1527
 l2cap_connect_cfm+0x35f/0x1120 net/bluetooth/l2cap_core.c:8392
 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 3456:
 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:1924 [inline]
 l2cap_sock_new_connection_cb+0xde/0x2a0 net/bluetooth/l2cap_sock.c:1512
 l2cap_connect_cfm+0x35f/0x1120 net/bluetooth/l2cap_core.c:8392
 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 4401:
 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:1492
 l2cap_sock_release+0x66/0x1e0 net/bluetooth/l2cap_sock.c:1453
 __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
 netlink_release+0x158e/0x19e0 net/netlink/af_netlink.c:799
 __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
 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: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

The buggy address belongs to the object at ffff888060f13000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1352 bytes inside of
 2048-byte region [ffff888060f13000, ffff888060f13800)

The buggy address belongs to the physical page:
page:ffffea000183c400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x60f10
head:ffffea000183c400 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea0001241800 dead000000000002 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 504, tgid 504 (kworker/0:4), ts 2464641313902, free_ts 2445851767263
 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:5657
 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
 __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:1303 [inline]
 mld_newpack+0x12f/0xc00 net/ipv6/mcast.c:1745
 add_grhead+0x5a/0x2a0 net/ipv6/mcast.c:1856
 add_grec+0x13b2/0x1660 net/ipv6/mcast.c:1994
 mld_send_cr net/ipv6/mcast.c:2120 [inline]
 mld_ifc_work+0x6e7/0xb40 net/ipv6/mcast.c:2658
 process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1486 [inline]
 free_pcp_prepare mm/page_alloc.c:1536 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3413
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3508
 free_slab mm/slub.c:2036 [inline]
 discard_slab mm/slub.c:2042 [inline]
 __unfreeze_partials+0x1a5/0x200 mm/slub.c:2591
 put_cpu_partial+0x17c/0x250 mm/slub.c:2667
 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:306
 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:3359 [inline]
 kmem_cache_alloc_node+0x14d/0x320 mm/slub.c:3404
 __alloc_skb+0xfc/0x7e0 net/core/skbuff.c:505
 alloc_skb include/linux/skbuff.h:1303 [inline]
 alloc_skb_with_frags+0xa7/0x710 net/core/skbuff.c:6164
 sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2755
 unix_dgram_sendmsg+0x539/0x16e0 net/unix/af_unix.c:1945
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 sock_write_iter+0x2d9/0x3e0 net/socket.c:1143
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x4b1/0xa30 fs/read_write.c:584
 ksys_write+0x14c/0x250 fs/read_write.c:637

Memory state around the buggy address:
 ffff888060f13400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888060f13480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888060f13500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff888060f13580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888060f13600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/17 00:51 linux-6.1.y f2ddafa93a25 0737c18f .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
2026/03/06 03:43 linux-6.1.y f2ddafa93a25 31e9c887 .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
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
2026/02/28 09:26 linux-6.1.y 779f9571ac3e 43249bac .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
2026/02/25 15:31 linux-6.1.y 779f9571ac3e 94a9671e .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
2026/02/21 23:47 linux-6.1.y 779f9571ac3e 6e7b5511 .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.