[PATCH] Bluetooth: hci_ldisc: Free rw_semaphore on close

[PATCH] Bluetooth: hci_ldisc: Free rw_semaphore on close

[Hermes Zhang]

From: Hermes Zhang <chenhuiz@axis.com>

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 <chenhuiz@axis.com>
---
 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

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

[Marcel Holtmann]

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 <chenhuiz@axis.com>
> ---
> drivers/bluetooth/hci_ldisc.c | 2 ++
> 1 file changed, 2 insertions(+)

patch has been applied to bluetooth-stable tree.

Regards

Marcel