linux-kernel - Re: [PATCH] tty: fix tty->ldisc leak on ENODEV from driver install

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Date:	Wed, 23 Mar 2011 10:49:53 +0200 (EET)
From:	Julian Anastasov <ja@....bg>
To:	Jiri Slaby <jslaby@...e.cz>
cc:	Greg Kroah-Hartman <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Jiri Slaby <jirislaby@...il.com>
Subject: Re: [PATCH] tty: fix tty->ldisc leak on ENODEV from driver install


 	Hello,

On Wed, 23 Mar 2011, Jiri Slaby wrote:

>> --- linux-2.6.38/drivers/tty/tty_io.c
>> +++ linux-2.6.38/drivers/tty/tty_io.c
>> @@ -188,6 +188,7 @@ void free_tty_struct(struct tty_struct *
>>  		put_device(tty->dev);
>>  	kfree(tty->write_buf);
>>  	tty_buffer_free_all(tty);
>> +	kfree(tty->ldisc);
>
> We should not mess up with ldisc here. We should call something like
> tty_ldisc_deinit from tty_init_dev on fail path. The deinit should drop
> the reference (call put_ldisc). Or maybe even deinitialize_tty_struct ->
> tty_ldisc_deinit -> put_ldisc).
>
> Note that your way you do not drop the module refcount of ld ops.

 	Right, that is what I found before going to sleep.
>From the visible functions I see that currently only
tty_ldisc_deref does exactly what we need. But I suspect
it should be used for other purposes. I assume the authors
have a better idea what to do here. Let me know if I need
to test a better patch.

>>  	kfree(tty);
>>  }
>
> regards,
> -- 
> js
> suse labs

Regards

--
Julian Anastasov <ja@....bg>
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