2018-08-28 01:48:30

by Hermes Zhang

Subject: [PATCH] Bluetooth: hci_ldisc: Free rw_semaphore on close

From: Hermes Zhang <[email protected]>

The percpu_rw_semaphore is not currently freed, and this leads to
a crash when the stale rcu callback is invoked. DEBUG_OBJECTS
detects this.

ODEBUG: free active (active state 1) object type: rcu_head hint: (null)
------------[ cut here ]------------
WARNING: CPU: 1 PID: 2024 at debug_print_object+0xac/0xc8
PC is at debug_print_object+0xac/0xc8
LR is at debug_print_object+0xac/0xc8
Call trace:
[<ffffff80082e2c2c>] debug_print_object+0xac/0xc8
[<ffffff80082e40b0>] debug_check_no_obj_freed+0x1e8/0x228
[<ffffff8008191254>] kfree+0x1cc/0x250
[<ffffff80083cc03c>] hci_uart_tty_close+0x54/0x108
[<ffffff800832e118>] tty_ldisc_close.isra.1+0x40/0x58
[<ffffff800832e14c>] tty_ldisc_kill+0x1c/0x40
[<ffffff800832e3dc>] tty_ldisc_release+0x94/0x170
[<ffffff8008325554>] tty_release_struct+0x1c/0x58
[<ffffff8008326400>] tty_release+0x3b0/0x490
[<ffffff80081a3fe8>] __fput+0x88/0x1d0
[<ffffff80081a418c>] ____fput+0xc/0x18
[<ffffff80080c0624>] task_work_run+0x9c/0xc0
[<ffffff80080a9e24>] do_exit+0x24c/0x8a0
[<ffffff80080aa4e0>] do_group_exit+0x38/0xa0
[<ffffff80080aa558>] __wake_up_parent+0x0/0x28
[<ffffff8008082c00>] el0_svc_naked+0x34/0x38
---[ end trace bfe08cbd89098cdf ]---

Signed-off-by: Hermes Zhang <[email protected]>
---
drivers/bluetooth/hci_ldisc.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 963bb0309e25..ea6238ed5c0e 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -543,6 +543,8 @@ static void hci_uart_tty_close(struct tty_struct *tty)
}
clear_bit(HCI_UART_PROTO_SET, &hu->flags);

+ percpu_free_rwsem(&hu->proto_lock);
+
kfree(hu);
}

--
2.11.0

2018-09-11 11:36:40

by Marcel Holtmann

Subject: Re: [PATCH] Bluetooth: hci_ldisc: Free rw_semaphore on close

Hi Hermes,

> The percpu_rw_semaphore is not currently freed, and this leads to
> a crash when the stale rcu callback is invoked. DEBUG_OBJECTS
> detects this.
>
> ODEBUG: free active (active state 1) object type: rcu_head hint: (null)
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 2024 at debug_print_object+0xac/0xc8
> PC is at debug_print_object+0xac/0xc8
> LR is at debug_print_object+0xac/0xc8
> Call trace:
> [<ffffff80082e2c2c>] debug_print_object+0xac/0xc8
> [<ffffff80082e40b0>] debug_check_no_obj_freed+0x1e8/0x228
> [<ffffff8008191254>] kfree+0x1cc/0x250
> [<ffffff80083cc03c>] hci_uart_tty_close+0x54/0x108
> [<ffffff800832e118>] tty_ldisc_close.isra.1+0x40/0x58
> [<ffffff800832e14c>] tty_ldisc_kill+0x1c/0x40
> [<ffffff800832e3dc>] tty_ldisc_release+0x94/0x170
> [<ffffff8008325554>] tty_release_struct+0x1c/0x58
> [<ffffff8008326400>] tty_release+0x3b0/0x490
> [<ffffff80081a3fe8>] __fput+0x88/0x1d0
> [<ffffff80081a418c>] ____fput+0xc/0x18
> [<ffffff80080c0624>] task_work_run+0x9c/0xc0
> [<ffffff80080a9e24>] do_exit+0x24c/0x8a0
> [<ffffff80080aa4e0>] do_group_exit+0x38/0xa0
> [<ffffff80080aa558>] __wake_up_parent+0x0/0x28
> [<ffffff8008082c00>] el0_svc_naked+0x34/0x38
> ---[ end trace bfe08cbd89098cdf ]---
>
> Signed-off-by: Hermes Zhang <[email protected]>
> ---
> drivers/bluetooth/hci_ldisc.c | 2 ++
> 1 file changed, 2 insertions(+)

patch has been applied to bluetooth-stable tree.

Regards

Marcel