KASAN: slab-use-after-free Read in l2cap_recv_acldata (2)

Status: fixed on 2026/01/07 12:29
Subsystems: bluetooth
[Documentation on labels]
Reported-by: syzbot+d32d77220b92eddd89ad@syzkaller.appspotmail.com
Fix commit: 79a2d4678ba9 Bluetooth: hci_core: lookup hci_conn on RX path on protocol side
First crash: 336d, last: 294d
▶ ▼ 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_recv_acldata bluetooth 19 1 770d 766d 0/29 auto-obsoleted due to no activity on 2024/10/07 16:15
upstream BUG: sleeping function called from invalid context in hci_cmd_sync_submit bluetooth 19 syz, C done done 3400 888d 1132d 0/29 auto-obsoleted due to no activity on 2024/05/13 05:09

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in l2cap_recv_acldata+0x78/0x1210 net/bluetooth/l2cap_core.c:7520
Read of size 8 at addr ffff88803ae3d198 by task kworker/u9:7/5815

CPU: 0 UID: 0 PID: 5815 Comm: kworker/u9:7 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: hci2 hci_rx_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 l2cap_recv_acldata+0x78/0x1210 net/bluetooth/l2cap_core.c:7520
 hci_acldata_packet net/bluetooth/hci_core.c:3861 [inline]
 hci_rx_work+0x5bb/0xe80 net/bluetooth/hci_core.c:4104
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 5815:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:417
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __kmalloc_cache_noprof+0x1ef/0x6c0 mm/slub.c:5755
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 __hci_conn_add+0x2b9/0x1b20 net/bluetooth/hci_conn.c:948
 le_conn_complete_evt+0x6d0/0x1500 net/bluetooth/hci_event.c:5659
 hci_le_conn_complete_evt+0x187/0x450 net/bluetooth/hci_event.c:5811
 hci_event_func net/bluetooth/hci_event.c:7556 [inline]
 hci_event_packet+0x78f/0x1200 net/bluetooth/hci_event.c:7613
 hci_rx_work+0x46a/0xe80 net/bluetooth/hci_core.c:4099
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 21332:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 __kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:587
 kasan_save_free_info mm/kasan/kasan.h:406 [inline]
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2530 [inline]
 slab_free mm/slub.c:6619 [inline]
 kfree+0x197/0x950 mm/slub.c:6826
 device_release+0x9c/0x1c0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x22b/0x480 lib/kobject.c:737
 hci_conn_put include/net/bluetooth/hci_core.h:1660 [inline]
 hci_disconnect_all_sync+0x1bd/0x350 net/bluetooth/hci_sync.c:5722
 hci_suspend_sync+0x3fc/0xc60 net/bluetooth/hci_sync.c:6197
 hci_suspend_dev+0x28d/0x4d0 net/bluetooth/hci_core.c:2849
 hci_suspend_notifier+0xf2/0x290 net/bluetooth/hci_core.c:2420
 notifier_call_chain+0x1b6/0x3e0 kernel/notifier.c:85
 notifier_call_chain_robust kernel/notifier.c:120 [inline]
 blocking_notifier_call_chain_robust+0x85/0x100 kernel/notifier.c:345
 pm_notifier_call_chain_robust+0x2c/0x60 kernel/power/main.c:103
 snapshot_open+0x1a2/0x280 kernel/power/user.c:77
 misc_open+0x2de/0x350 drivers/char/misc.c:163
 chrdev_open+0x4cf/0x5e0 fs/char_dev.c:414
 do_dentry_open+0x9b1/0x1350 fs/open.c:965
 vfs_open+0x3b/0x350 fs/open.c:1097
 do_open fs/namei.c:3975 [inline]
 path_openat+0x2ef1/0x3840 fs/namei.c:4134
 do_filp_open+0x1fa/0x410 fs/namei.c:4161
 do_sys_openat2+0x121/0x1c0 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1463
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88803ae3c000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 4504 bytes inside of
 freed 8192-byte region [ffff88803ae3c000, ffff88803ae3e000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3ae38
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88813ff27280 ffffea0001876600 dead000000000002
raw: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88813ff27280 ffffea0001876600 dead000000000002
head: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 0080000000000003 ffffea0000eb8e01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 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 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5620, tgid 5620 (dhcpcd-run-hook), ts 72903299903, free_ts 72810702292
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1850
 prep_new_page mm/page_alloc.c:1858 [inline]
 get_page_from_freelist+0x28c0/0x2960 mm/page_alloc.c:3884
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5183
 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:3046 [inline]
 allocate_slab+0x96/0x3a0 mm/slub.c:3219
 new_slab mm/slub.c:3273 [inline]
 ___slab_alloc+0xb12/0x13f0 mm/slub.c:4643
 __slab_alloc+0xc6/0x1f0 mm/slub.c:4762
 __slab_alloc_node mm/slub.c:4838 [inline]
 slab_alloc_node mm/slub.c:5260 [inline]
 __kmalloc_cache_noprof+0xec/0x6c0 mm/slub.c:5750
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 tomoyo_print_bprm security/tomoyo/audit.c:26 [inline]
 tomoyo_init_log+0x1120/0x1f70 security/tomoyo/audit.c:264
 tomoyo_supervisor+0x340/0x1480 security/tomoyo/common.c:2198
 tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
 tomoyo_env_perm+0x149/0x1e0 security/tomoyo/environ.c:63
 tomoyo_environ security/tomoyo/domain.c:672 [inline]
 tomoyo_find_next_domain+0x15d1/0x1aa0 security/tomoyo/domain.c:888
 tomoyo_bprm_check_security+0x11d/0x180 security/tomoyo/tomoyo.c:102
 security_bprm_check+0x89/0x270 security/security.c:1341
 search_binary_handler fs/exec.c:1660 [inline]
 exec_binprm fs/exec.c:1702 [inline]
 bprm_execve+0x8ee/0x1450 fs/exec.c:1754
 do_execveat_common+0x510/0x6a0 fs/exec.c:1860
page last free pid 5615 tgid 5615 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1394 [inline]
 __free_frozen_pages+0xfb6/0x1140 mm/page_alloc.c:2906
 discard_slab mm/slub.c:3317 [inline]
 __put_partials+0x149/0x170 mm/slub.c:3864
 __slab_free+0x29e/0x370 mm/slub.c:5913
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:352
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4962 [inline]
 slab_alloc_node mm/slub.c:5272 [inline]
 kmem_cache_alloc_noprof+0x181/0x6b0 mm/slub.c:5279
 getname_flags+0xb8/0x540 fs/namei.c:146
 getname include/linux/fs.h:2922 [inline]
 do_sys_openat2+0xbc/0x1c0 fs/open.c:1431
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1463
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88803ae3d080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803ae3d100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88803ae3d180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88803ae3d200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803ae3d280: 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
2025/10/19 13:06 upstream 1c64efcb083c 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in l2cap_recv_acldata
2025/09/09 09:15 upstream f777d1112ee5 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in l2cap_recv_acldata
2025/09/06 20:58 upstream b236920731dd d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in l2cap_recv_acldata
* Struck through repros no longer work on HEAD.