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Tue, 06 Oct 2026 07:45:58 -0700 (PDT) From: Cen Zhang To: marcel@holtmann.org, luiz.dentz@gmail.com Cc: linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, jjzuming@gmail.com, zzzccc427@gmail.com Subject: [PATCH] Bluetooth: ISO: Hold the listener during disconnect notification Date: Tue, 6 Oct 2026 22:45:53 +0800 Message-Id: X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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: 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 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 --- 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); }