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KASAN: slab-use-after-free Read in l2cap_disconn_ind (3)

Status: upstream: reported on 2026/05/13 08:12
Subsystems: bluetooth
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+9c40ad7c6ed7165e46e8@syzkaller.appspotmail.com
First crash: 34d, last: 34d
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
1b93e63d-590f-4831-a0dd-de46c3707b3f repro-c 💥 KASAN: slab-use-after-free Read in l2cap_disconn_ind (3) 2026/05/25 10:25 2026/05/25 10:43 2026/05/25 17:16 c69befb30ac10e158cc9d1557b508ee3f0eca1de DoWhile loop is going in cycles for 20 iterations
0eb3bda0-63d2-48dd-8fad-d81d8b25b3f4 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ✅ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in l2cap_disconn_ind (3) 2026/05/24 16:24 2026/05/24 16:24 2026/05/24 17:13 c69befb30ac10e158cc9d1557b508ee3f0eca1de
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [bluetooth?] KASAN: slab-use-after-free Read in l2cap_disconn_ind (3) 0 (1) 2026/05/13 08:12
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in l2cap_disconn_ind (2) bluetooth 19 6 217d 252d 0/29 auto-obsoleted due to no activity on 2026/02/16 10:02
upstream KASAN: slab-use-after-free Read in l2cap_disconn_ind bluetooth 19 2 497d 568d 0/29 auto-obsoleted due to no activity on 2025/05/12 10:49

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in l2cap_disconn_ind+0xd7/0xf0 net/bluetooth/l2cap_core.c:7430
Read of size 1 at addr ffff88807ee53278 by task kworker/u9:1/4933

CPU: 1 UID: 0 PID: 4933 Comm: kworker/u9:1 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: hci2 hci_conn_timeout
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
 l2cap_disconn_ind+0xd7/0xf0 net/bluetooth/l2cap_core.c:7430
 hci_proto_disconn_ind include/net/bluetooth/hci_core.h:2115 [inline]
 hci_conn_timeout+0x1dc/0x230 net/bluetooth/hci_conn.c:646
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3302
 process_scheduled_works kernel/workqueue.c:3385 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3466
 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
 </TASK>

Allocated by task 16760:
 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]
 l2cap_conn_add.part.0+0x60/0xb00 net/bluetooth/l2cap_core.c:7001
 l2cap_conn_add include/net/bluetooth/l2cap.h:840 [inline]
 l2cap_chan_connect+0x1435/0x1f90 net/bluetooth/l2cap_core.c:7192
 l2cap_sock_connect+0x37a/0x770 net/bluetooth/l2cap_sock.c:256
 __sys_connect_file+0x141/0x1a0 net/socket.c:2148
 __sys_connect+0x141/0x170 net/socket.c:2167
 __do_sys_connect net/socket.c:2173 [inline]
 __se_sys_connect net/socket.c:2170 [inline]
 __x64_sys_connect+0x72/0xb0 net/socket.c:2170
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 16756:
 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:6250 [inline]
 kfree+0x223/0x6c0 mm/slub.c:6565
 l2cap_conn_free net/bluetooth/l2cap_core.c:1823 [inline]
 kref_put include/linux/kref.h:65 [inline]
 l2cap_conn_put net/bluetooth/l2cap_core.c:1835 [inline]
 l2cap_conn_del+0x57f/0x710 net/bluetooth/l2cap_core.c:1815
 l2cap_connect_cfm+0x9bb/0xf80 net/bluetooth/l2cap_core.c:7374
 hci_connect_cfm include/net/bluetooth/hci_core.h:2139 [inline]
 hci_conn_failed+0x188/0x360 net/bluetooth/hci_conn.c:1409
 hci_abort_conn_sync+0x7d9/0xb20 net/bluetooth/hci_sync.c:5763
 hci_disconnect_all_sync.constprop.0.isra.0+0x155/0x430 net/bluetooth/hci_sync.c:5786
 hci_suspend_sync+0x8b7/0xa70 net/bluetooth/hci_sync.c:6262
 hci_suspend_dev+0x31d/0x540 net/bluetooth/hci_core.c:2850
 hci_suspend_notifier+0x21e/0x330 net/bluetooth/hci_core.c:2421
 notifier_call_chain+0x99/0x400 kernel/notifier.c:85
 notifier_call_chain_robust kernel/notifier.c:120 [inline]
 blocking_notifier_call_chain_robust kernel/notifier.c:345 [inline]
 blocking_notifier_call_chain_robust+0xc8/0x160 kernel/notifier.c:333
 pm_notifier_call_chain_robust+0x27/0x60 kernel/power/main.c:172
 snapshot_open+0x189/0x2a0 kernel/power/user.c:77
 misc_open+0x26d/0x450 drivers/char/misc.c:163
 chrdev_open+0x234/0x6a0 fs/char_dev.c:411
 do_dentry_open+0x6d8/0x1660 fs/open.c:947
 vfs_open+0x82/0x3f0 fs/open.c:1079
 do_open fs/namei.c:4699 [inline]
 path_openat+0x208c/0x31a0 fs/namei.c:4858
 do_file_open+0x20e/0x430 fs/namei.c:4887
 do_sys_openat2+0x10d/0x1e0 fs/open.c:1364
 do_sys_open fs/open.c:1370 [inline]
 __do_sys_openat fs/open.c:1386 [inline]
 __se_sys_openat fs/open.c:1381 [inline]
 __x64_sys_openat+0x12d/0x210 fs/open.c:1381
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807ee53000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 632 bytes inside of
 freed 1024-byte region [ffff88807ee53000, ffff88807ee53400)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7ee50
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 ffff88813fe34dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813fe34dc0 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1151, tgid 1151 (kworker/u8:8), ts 131280693452, free_ts 131177469088
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x153/0x170 mm/page_alloc.c:1858
 prep_new_page mm/page_alloc.c:1866 [inline]
 get_page_from_freelist+0x11a6/0x33b0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5226
 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:7255
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x375/0x650 mm/slub.c:4651
 alloc_from_pcs mm/slub.c:4749 [inline]
 slab_alloc_node mm/slub.c:4883 [inline]
 __do_kmalloc_node mm/slub.c:5294 [inline]
 __kmalloc_noprof+0x688/0x850 mm/slub.c:5307
 kmalloc_noprof include/linux/slab.h:954 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 neigh_alloc net/core/neighbour.c:521 [inline]
 ___neigh_create+0x1545/0x2950 net/core/neighbour.c:655
 ip6_finish_output2+0xffa/0x1ce0 net/ipv6/ip6_output.c:128
 __ip6_finish_output+0x357/0xdf0 net/ipv6/ip6_output.c:208
 ip6_finish_output net/ipv6/ip6_output.c:219 [inline]
 NF_HOOK_COND include/linux/netfilter.h:307 [inline]
 ip6_output+0x2aa/0xa60 net/ipv6/ip6_output.c:246
 dst_output include/net/dst.h:470 [inline]
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ndisc_send_skb+0xa85/0x1bf0 net/ipv6/ndisc.c:512
 ndisc_send_rs+0x129/0x680 net/ipv6/ndisc.c:723
 addrconf_rs_timer+0x424/0x880 net/ipv6/addrconf.c:4049
 call_timer_fn+0x19a/0x640 kernel/time/timer.c:1748
 expire_timers kernel/time/timer.c:1799 [inline]
 __run_timers+0x75f/0xaf0 kernel/time/timer.c:2374
page last free pid 5637 tgid 5637 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1402 [inline]
 __free_frozen_pages+0x747/0x1040 mm/page_alloc.c:2943
 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:4569 [inline]
 slab_alloc_node mm/slub.c:4898 [inline]
 kmem_cache_alloc_noprof+0x241/0x6e0 mm/slub.c:4905
 alloc_filename fs/namei.c:142 [inline]
 do_getname+0x35/0x390 fs/namei.c:182
 getname include/linux/fs.h:2526 [inline]
 class_filename_constructor include/linux/fs.h:2553 [inline]
 do_sys_openat2+0xc5/0x1e0 fs/open.c:1363
 do_sys_open fs/open.c:1370 [inline]
 __do_sys_openat fs/open.c:1386 [inline]
 __se_sys_openat fs/open.c:1381 [inline]
 __x64_sys_openat+0x12d/0x210 fs/open.c:1381
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88807ee53100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807ee53180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807ee53200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff88807ee53280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807ee53300: 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
2026/05/10 03:16 upstream 1bfaee9d3351 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in l2cap_disconn_ind
* Struck through repros no longer work on HEAD.