Re: tty_register_device NULL pointer dereference in 2.6.31-rc4

Dave Young
2009-07-27T09:59:05Z

On Sat, Jul 25, 2009 at 01:10:46PM +0100, Alan Cox wrote:
> > > tty_register_device appears to have been called with a NULL pointer. Not
> > > sure why however.
> >
> > if that is the pointer for the struct device, then that used to be fine
> > in the past. Not all RFCOMM device have a parent when they are created.
>
> The tty layer doesn't care about the struct device really. Nothing there
> has changed. The NULL passed appears to be the driver argument.

Agree with you, because in rfcomm_init, rfcomm thread run before tty initilized, the following patch may fix the problem. oliver, could you verify it it fix your problem?
---

rfcomm tty may be used before rfcomm_tty_driver initilized,

reporting in:
http://marc.info/?l=linux-bluetooth&m=124404919324542&w=2

make 3 changes:
1. remove #ifdef in rfcomm/core.c,
make it blank function when rfcomm tty not selected in rfcomm.h

2. tune the rfcomm_init error patch to ensure
tty driver initilized before any usage.

3. remove __exit for rfcomm_cleanup_sockets
because above change need call it in a __init function.

CC: Alan Cox <alan@lxorguk.ukuu.org.uk>
Reported-by: Oliver Hartkopp <oliver@hartkopp.net>
Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
--
include/net/bluetooth/rfcomm.h | 13 ++++++++++++-
net/bluetooth/rfcomm/core.c | 31 +++++++++++++++++++++----------
net/bluetooth/rfcomm/sock.c | 2 +-
3 files changed, 34 insertions(+), 12 deletions(-)

--- linux-2.6.orig/include/net/bluetooth/rfcomm.h 2009-04-09 16:23:03.000000000 +0800
+++ linux-2.6/include/net/bluetooth/rfcomm.h 2009-07-27 17:14:43.000000000 +0800
@@ -355,7 +355,18 @@ struct rfcomm_dev_list_req {
};

int rfcomm_dev_ioctl(struct sock *sk, unsigned int cmd, void __user *arg);
+
+#ifdef CONFIG_BT_RFCOMM_TTY
int rfcomm_init_ttys(void);
void rfcomm_cleanup_ttys(void);
-
+#else
+static inline int rfcomm_init_ttys(void)
+{
+ return 0;
+}
+static inline int rfcomm_cleanup_ttys(void)
+{
+ return 0;
+}
+#endif
#endif /* __RFCOMM_H */
--- linux-2.6.orig/net/bluetooth/rfcomm/core.c 2009-06-16 17:39:32.000000000 +0800
+++ linux-2.6/net/bluetooth/rfcomm/core.c 2009-07-27 17:24:27.000000000 +0800
@@ -2080,28 +2080,41 @@ static CLASS_ATTR(rfcomm_dlc, S_IRUGO, r
/* ---- Initialization ---- */
static int __init rfcomm_init(void)
{
+ int ret;
+
l2cap_load();

+ ret = rfcomm_init_sockets();
+ if (ret)
+ goto out_sock;
+
+ ret = rfcomm_init_ttys();
+ if (ret)
+ goto out_tty;
+
hci_register_cb(&rfcomm_cb);

rfcomm_thread = kthread_run(rfcomm_run, NULL, "krfcommd");
if (IS_ERR(rfcomm_thread)) {
- hci_unregister_cb(&rfcomm_cb);
- return PTR_ERR(rfcomm_thread);
+ ret = PTR_ERR(rfcomm_thread);
+ goto out_thread;
}

if (class_create_file(bt_class, &class_attr_rfcomm_dlc) < 0)
BT_ERR("Failed to create RFCOMM info file");

- rfcomm_init_sockets();
-
-#ifdef CONFIG_BT_RFCOMM_TTY
- rfcomm_init_ttys();
-#endif
-
BT_INFO("RFCOMM ver %s", VERSION);

return 0;
+
+out_thread:
+ hci_unregister_cb(&rfcomm_cb);
+out_tty:
+ rfcomm_cleanup_ttys();
+out_sock:
+ rfcomm_cleanup_sockets();
+
+ return ret;
}

static void __exit rfcomm_exit(void)
@@ -2112,9 +2125,7 @@ static void __exit rfcomm_exit(void)

kthread_stop(rfcomm_thread);

-#ifdef CONFIG_BT_RFCOMM_TTY
rfcomm_cleanup_ttys();
-#endif

rfcomm_cleanup_sockets();
}
--- linux-2.6.orig/net/bluetooth/rfcomm/sock.c 2009-04-09 16:23:04.000000000 +0800
+++ linux-2.6/net/bluetooth/rfcomm/sock.c 2009-07-27 17:39:43.000000000 +0800
@@ -1132,7 +1132,7 @@ error:
return err;
}

-void __exit rfcomm_cleanup_sockets(void)
+void rfcomm_cleanup_sockets(void)
{
class_remove_file(bt_class, &class_attr_rfcomm);