Hello maintainers,
I would like to report a use-after-free (UAF) vulnerability
identified in the Bluetooth SCO (Synchronous Connection
Oriented) connection handling code using
our customized syzkaller on 6.17.0-rc5.
The bug occurs due to concurrent access to freed
sco_conn structures during connection failure scenarios.
After my superficial analysis, the situation when race occurs may be as follows:
CONCURRENT CLEANUP PATHS:
- Path A: Socket close operation (Task 31374) triggers sco_sock_release()
- Path B: HCI connection failure triggers hci_abort_conn_sync() in
workqueue (Task 352)
RACE CONDITION SEQUENCE:
a) Task 31374 releases socket, eventually leading to sco_conn_free()
b) sco_conn_free() sets hcon->sco_data = NULL and calls kfree(conn)
c) Task 352 (workqueue) executes hci_conn_failed() -> sco_connect_cfm()
d) sco_connect_cfm() calls sco_conn_del(hcon, bt_to_errno(status))
e) sco_conn_del() attempts to access already-freed sco_conn via
hcon->sco_data
The detail KASAN report as follow:
==================================================================
BUG: KASAN: slab-use-after-free in sco_conn_free net/bluetooth/sco.c:87 [inline]
BUG: KASAN: slab-use-after-free in kref_put include/linux/kref.h:65 [inline]
BUG: KASAN: slab-use-after-free in sco_conn_put+0xdd/0x410
net/bluetooth/sco.c:107
Write of size 8 at addr ffff88811cb96b50 by task kworker/u17:4/352
CPU: 1 UID: 0 PID: 352 Comm: kworker/u17:4 Not tainted
6.17.0-rc5-g717368f83676 #4 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Workqueue: hci13 hci_cmd_sync_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x10b/0x170 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0x191/0x550 mm/kasan/report.c:482
kasan_report+0xc4/0x100 mm/kasan/report.c:595
sco_conn_free net/bluetooth/sco.c:87 [inline]
kref_put include/linux/kref.h:65 [inline]
sco_conn_put+0xdd/0x410 net/bluetooth/sco.c:107
sco_connect_cfm+0xb4/0xae0 net/bluetooth/sco.c:1441
hci_connect_cfm include/net/bluetooth/hci_core.h:2082 [inline]
hci_conn_failed+0x20a/0x2e0 net/bluetooth/hci_conn.c:1313
hci_conn_unlink+0x55f/0x810 net/bluetooth/hci_conn.c:1121
hci_conn_del+0xb6/0x1110 net/bluetooth/hci_conn.c:1147
hci_abort_conn_sync+0x8c5/0xbb0 net/bluetooth/hci_sync.c:5689
hci_cmd_sync_work+0x281/0x380 net/bluetooth/hci_sync.c:332
process_one_work kernel/workqueue.c:3236 [inline]
process_scheduled_works+0x77e/0x1040 kernel/workqueue.c:3319
worker_thread+0xbee/0x1200 kernel/workqueue.c:3400
kthread+0x3c7/0x870 kernel/kthread.c:463
ret_from_fork+0x13a/0x1e0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Allocated by task 31370:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x30/0x70 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:388 [inline]
__kasan_kmalloc+0x82/0x90 mm/kasan/common.c:405
kasan_kmalloc include/linux/kasan.h:260 [inline]
__do_kmalloc_node mm/slub.c:4382 [inline]
__kmalloc_noprof+0x22f/0x390 mm/slub.c:4394
kmalloc_noprof include/linux/slab.h:909 [inline]
sk_prot_alloc+0xae/0x220 net/core/sock.c:2239
sk_alloc+0x34/0x5a0 net/core/sock.c:2295
bt_sock_alloc+0x3c/0x330 net/bluetooth/af_bluetooth.c:151
sco_sock_alloc net/bluetooth/sco.c:562 [inline]
sco_sock_create+0xc0/0x350 net/bluetooth/sco.c:593
bt_sock_create+0x161/0x3b0 net/bluetooth/af_bluetooth.c:135
__sock_create+0x3ad/0x780 net/socket.c:1589
sock_create net/socket.c:1647 [inline]
__sys_socket_create net/socket.c:1684 [inline]
__sys_socket+0xd5/0x330 net/socket.c:1731
__do_sys_socket net/socket.c:1745 [inline]
__se_sys_socket net/socket.c:1743 [inline]
__x64_sys_socket+0x7a/0x90 net/socket.c:1743
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc7/0x240 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 31374:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x30/0x70 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:243 [inline]
__kasan_slab_free+0x3d/0x50 mm/kasan/common.c:275
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2428 [inline]
slab_free mm/slub.c:4701 [inline]
kfree+0x199/0x3b0 mm/slub.c:4900
sk_prot_free net/core/sock.c:2278 [inline]
__sk_destruct+0x4aa/0x630 net/core/sock.c:2373
sco_sock_release+0x2ad/0x300 net/bluetooth/sco.c:1333
__sock_release net/socket.c:649 [inline]
sock_close+0xb8/0x230 net/socket.c:1439
__fput+0x3d1/0x9e0 fs/file_table.c:468
task_work_run+0x206/0x2a0 kernel/task_work.c:227
get_signal+0x1201/0x1410 kernel/signal.c:2807
arch_do_signal_or_restart+0x34/0x740 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop+0x68/0xc0 kernel/entry/common.c:40
exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
do_syscall_64+0x1dd/0x240 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff88811cb96800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 848 bytes inside of
freed 1024-byte region [ffff88811cb96800, ffff88811cb96c00)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11cb90
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x200000000000040(head|node=0|zone=2)
page_type: f5(slab)
raw: 0200000000000040 ffff888100042dc0 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 0200000000000040 ffff888100042dc0 dead000000000122 0000000000000000
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 0200000000000003 ffffea000472e401 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88811cb96a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88811cb96a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88811cb96b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88811cb96b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88811cb96c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
Best regards,
Cen Zhang
