* [PATCH] Bluetooth: ISO: Hold the listener during disconnect notification
@ 2026-10-06 14:45 Cen Zhang
0 siblings, 0 replies; only message in thread
From: Cen Zhang @ 2026-10-06 14:45 UTC (permalink / raw)
To: marcel, luiz.dentz
Cc: linux-bluetooth, linux-kernel, baijiaju1990, jjzuming, zzzccc427
An ISO listener must remain alive until a queued child's disconnect
notification completes. bt_accept_enqueue() retains only the child and
stores a raw parent pointer; iso_conn_ready() drops its temporary
listener reference after setup. iso_chan_del() saves that pointer,
unlinks the child and then calls parent->sk_data_ready() without holding
a listener reference.
With an incoming CIS child still queued, disconnect and listener release
can proceed in this order:
HCI disconnect Listener release
iso_conn_del(): lock child
iso_chan_del(): save parent
bt_accept_unlink(child)
iso_sock_cleanup_listen():
drain empty accept queue
iso_sock_release():
orphan and kill listener
final sock_put(listener)
parent->sk_data_ready(parent)
After unlink, listener cleanup no longer has to take the child socket
lock. The listener can therefore be freed before iso_chan_del() reads
sk_data_ready, causing a use-after-free.
Take a temporary parent reference before bt_accept_unlink() and drop it
after the notification. The child lock excludes accept dequeue while the
child is still queued, so listener cleanup cannot complete before
sock_hold(). The reference then keeps the listener alive across unlink
and through the callback without changing lock order.
KASAN report as below:
==================================================================
BUG: KASAN: slab-use-after-free in iso_chan_del+0x302/0x320
Read of size 8 at addr ffff888105ca2188 by task kworker/2:1/50
CPU: 2 UID: 0 PID: 50 Comm: kworker/2:1 Not tainted
7.2.0-rc6-pmb-bt-functional-v1+ #1 PREEMPT(lazy)
Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps
fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events iso_fixture_disconnect_work
Call Trace:
<TASK>
dump_stack_lvl+0x93/0xd0
print_report+0xce/0x630
? iso_chan_del+0x302/0x320
? srso_alias_return_thunk+0x5/0xfbef5
? __virt_addr_valid+0x20d/0x410
? iso_chan_del+0x302/0x320
kasan_report+0xe0/0x110
? iso_chan_del+0x302/0x320
iso_chan_del+0x302/0x320
iso_conn_del+0x19d/0x3c0
? __pfx_iso_disconn_cfm+0x10/0x10
iso_disconn_cfm+0x78/0x120
hci_disconn_complete_evt+0x319/0xa30
? find_held_lock+0x2b/0x80
hci_test_iso_disconn_event+0x85/0xb0
? __pfx_hci_test_iso_disconn_event+0x10/0x10
? srso_alias_return_thunk+0x5/0xfbef5
? srso_alias_return_thunk+0x5/0xfbef5
? _raw_read_unlock+0x23/0x40
? srso_alias_return_thunk+0x5/0xfbef5
? __hci_dev_get+0x15d/0x280
iso_fixture_disconnect_work+0x67/0x290
process_one_work+0x908/0x19c0
? __pfx_process_one_work+0x10/0x10
? srso_alias_return_thunk+0x5/0xfbef5
? lock_is_held_type+0x8f/0x100
? srso_alias_return_thunk+0x5/0xfbef5
worker_thread+0x65c/0xe40
? srso_alias_return_thunk+0x5/0xfbef5
? __kthread_parkme+0x175/0x220
? srso_alias_return_thunk+0x5/0xfbef5
? __pfx_worker_thread+0x10/0x10
kthread+0x34f/0x460
? srso_alias_return_thunk+0x5/0xfbef5
? __pfx_kthread+0x10/0x10
ret_from_fork+0x659/0x940
? __pfx_ret_from_fork+0x10/0x10
? srso_alias_return_thunk+0x5/0xfbef5
? __switch_to+0x74f/0xf80
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
Allocated by task 521:
kasan_save_stack+0x33/0x60
kasan_save_track+0x14/0x30
__kasan_kmalloc+0xaa/0xb0
__kmalloc_noprof+0x2d7/0x770
sk_prot_alloc+0x13e/0x260
sk_alloc+0x37/0xb40
bt_sock_alloc+0x40/0x3b0
iso_sock_alloc.constprop.0+0x3a/0x360
iso_sock_create+0xc7/0x160
bt_sock_create+0x171/0x330
__sock_create+0x2c4/0x730
__sys_socket+0x141/0x210
__x64_sys_socket+0x77/0xc0
do_syscall_64+0x115/0x6a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 521:
kasan_save_stack+0x33/0x60
kasan_save_track+0x14/0x30
kasan_save_free_info+0x3b/0x60
__kasan_slab_free+0x5f/0x80
kfree+0x307/0x580
__sk_destruct+0x64f/0x790
sk_destruct+0xb3/0xd0
__sk_free+0xdd/0x370
sk_free+0x51/0x80
iso_sock_release+0x46d/0x5b0
__sock_release+0xb8/0x270
sock_close+0x21/0x30
__fput+0x39f/0xa60
task_work_run+0x144/0x230
do_exit+0x834/0x2830
do_group_exit+0xc7/0x280
get_signal+0x20a9/0x2400
arch_do_signal_or_restart+0x94/0x6f0
exit_to_user_mode_loop+0xcf/0x570
do_syscall_64+0x4f0/0x6a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff888105ca2000
which
belongs to the cache kmalloc-2k of size
2048
The buggy address is located 392 bytes inside of
freed
2048-byte region [ffff888105ca2000,
ffff888105ca2800)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000
index:0xffff888105ca5000 pfn:0x105ca0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x200000000000240(workingset|head|node=0|zone=2)
page_type: f5(slab)
raw: 0200000000000240 ffff888100042f00 ffffea00042cd010
ffffea00042c9210
raw: ffff888105ca5000 0000000000080005 00000000f5000000
0000000000000000
head: 0200000000000240 ffff888100042f00 ffffea00042cd010
ffffea00042c9210
head: ffff888105ca5000 0000000000080005 00000000f5000000
0000000000000000
head: 0200000000000003 fffffffffffffe01 00000000ffffffff
00000000ffffffff
head: ffff888105ca1000 0000000000000000 00000000ffffffff
0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888105ca2080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888105ca2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888105ca2180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888105ca2200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888105ca2280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Fixes: f764a6c2c1e4 ("Bluetooth: ISO: Add broadcast support")
Assisted-by: LLM
Signed-off-by: Cen Zhang <zzzccc427@gmail.com>
---
diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index e52bd59ba1b3e3536a0c6017702487924c8513b5..971e02fd672ba5d8009b7a274654d5c84bb26080 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -286,8 +286,11 @@ static void iso_chan_del(struct sock *sk, int err)
parent = bt_sk(sk)->parent;
if (parent) {
+ /* Unlinking the child allows the parent to be freed. */
+ sock_hold(parent);
bt_accept_unlink(sk);
parent->sk_data_ready(parent);
+ sock_put(parent);
} else {
sk->sk_state_change(sk);
}
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