Hi Dmitry, On Fri, Oct 25, 2024 at 7:40 AM Dmitry Antipov <dmantipov@xxxxxxxxx> wrote: > > Syzbot has reported the following KASAN splat: > > BUG: KASAN: slab-use-after-free in device_for_each_child+0x18f/0x1a0 > Read of size 8 at addr ffff88801f605308 by task kbnepd bnep0/4980 > > CPU: 0 UID: 0 PID: 4980 Comm: kbnepd bnep0 Not tainted 6.12.0-rc4-00161-gae90f6a6170d #1 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-2.fc40 04/01/2014 > Call Trace: > <TASK> > dump_stack_lvl+0x100/0x190 > ? device_for_each_child+0x18f/0x1a0 > print_report+0x13a/0x4cb > ? __virt_addr_valid+0x5e/0x590 > ? __phys_addr+0xc6/0x150 > ? device_for_each_child+0x18f/0x1a0 > kasan_report+0xda/0x110 > ? device_for_each_child+0x18f/0x1a0 > ? __pfx_dev_memalloc_noio+0x10/0x10 > device_for_each_child+0x18f/0x1a0 > ? __pfx_device_for_each_child+0x10/0x10 > pm_runtime_set_memalloc_noio+0xf2/0x180 > netdev_unregister_kobject+0x1ed/0x270 > unregister_netdevice_many_notify+0x123c/0x1d80 > ? __mutex_trylock_common+0xde/0x250 > ? __pfx_unregister_netdevice_many_notify+0x10/0x10 > ? trace_contention_end+0xe6/0x140 > ? __mutex_lock+0x4e7/0x8f0 > ? __pfx_lock_acquire.part.0+0x10/0x10 > ? rcu_is_watching+0x12/0xc0 > ? unregister_netdev+0x12/0x30 > unregister_netdevice_queue+0x30d/0x3f0 > ? __pfx_unregister_netdevice_queue+0x10/0x10 > ? __pfx_down_write+0x10/0x10 > unregister_netdev+0x1c/0x30 > bnep_session+0x1fb3/0x2ab0 > ? __pfx_bnep_session+0x10/0x10 > ? __pfx_lock_release+0x10/0x10 > ? __pfx_woken_wake_function+0x10/0x10 > ? __kthread_parkme+0x132/0x200 > ? __pfx_bnep_session+0x10/0x10 > ? kthread+0x13a/0x370 > ? __pfx_bnep_session+0x10/0x10 > kthread+0x2b7/0x370 > ? __pfx_kthread+0x10/0x10 > ret_from_fork+0x48/0x80 > ? __pfx_kthread+0x10/0x10 > ret_from_fork_asm+0x1a/0x30 > </TASK> > > Allocated by task 4974: > kasan_save_stack+0x30/0x50 > kasan_save_track+0x14/0x30 > __kasan_kmalloc+0xaa/0xb0 > __kmalloc_noprof+0x1d1/0x440 > hci_alloc_dev_priv+0x1d/0x2820 > __vhci_create_device+0xef/0x7d0 > vhci_write+0x2c7/0x480 > vfs_write+0x6a0/0xfc0 > ksys_write+0x12f/0x260 > do_syscall_64+0xc7/0x250 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > Freed by task 4979: > kasan_save_stack+0x30/0x50 > kasan_save_track+0x14/0x30 > kasan_save_free_info+0x3b/0x60 > __kasan_slab_free+0x4f/0x70 > kfree+0x141/0x490 > hci_release_dev+0x4d9/0x600 > bt_host_release+0x6a/0xb0 > device_release+0xa4/0x240 > kobject_put+0x1ec/0x5a0 > put_device+0x1f/0x30 > vhci_release+0x81/0xf0 > __fput+0x3f6/0xb30 > task_work_run+0x151/0x250 > do_exit+0xa79/0x2c30 > do_group_exit+0xd5/0x2a0 > get_signal+0x1fcd/0x2210 > arch_do_signal_or_restart+0x93/0x780 > syscall_exit_to_user_mode+0x140/0x290 > do_syscall_64+0xd4/0x250 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > Fix this by doing 'device_del()' later and immediately before > freeing its 'struct hci_dev' container. Otherwise the former > might race against 'unregister_netdev()' innards called when > 'bnep_session()' is going to terminate. > > Reported-by: syzbot+6cf5652d3df49fae2e3f@xxxxxxxxxxxxxxxxxxxxxxxxx > Closes: https://syzkaller.appspot.com/bug?extid=6cf5652d3df49fae2e3f > Fixes: bdc3e0f1d201 ("Bluetooth: Move device_add handling into hci_register_dev") > Signed-off-by: Dmitry Antipov <dmantipov@xxxxxxxxx> > --- > net/bluetooth/hci_core.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c > index 96d097b21d13..f1195b110495 100644 > --- a/net/bluetooth/hci_core.c > +++ b/net/bluetooth/hci_core.c > @@ -2716,7 +2716,6 @@ void hci_unregister_dev(struct hci_dev *hdev) > rfkill_destroy(hdev->rfkill); > } > > - device_del(&hdev->dev); > /* Actual cleanup is deferred until hci_release_dev(). */ > hci_dev_put(hdev); > } > @@ -2756,6 +2755,8 @@ void hci_release_dev(struct hci_dev *hdev) > kfree_skb(hdev->sent_cmd); > kfree_skb(hdev->req_skb); > kfree_skb(hdev->recv_event); > + > + device_del(&hdev->dev); This actually doesn't work, we depend on device_del for hci_release_dev to be called, so as the result hdev are never freed with this change. > kfree(hdev); > } > EXPORT_SYMBOL(hci_release_dev); > -- > 2.47.0 > -- Luiz Augusto von Dentz
