linux-kernel - Re: [PATCH] tty fix oops when rmmod 8250

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Date:   Mon, 18 Sep 2017 10:43:12 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     nixiaoming <nixiaoming@...wei.com>, adobriyan@...il.com,
        torvalds@...ux-foundation.org, gregkh@...uxfoundation.org,
        viro@...iv.linux.org.uk
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH] tty fix oops when rmmod 8250

On 09/15/2017, 11:45 AM, nixiaoming wrote:
> After rmmod 8250.ko
> tty_kref_put starts kwork (release_one_tty) to release proc interface

I believe you wanted to add a period here.

> oops when accessing driver->driver_name in proc_tty_unregister_driver

"The kernel oopses when"... ?

> Use jprobe, found driver->driver_name point to 8250.ko
> static static struct uart_driver serial8250_reg
> .driver_name= serial,
> 
> Use name in proc_dir_entry instead of driver->driver_name to fix oops
> 
> test on linux 4.1.12:
...
> @@ -164,7 +165,7 @@ void proc_tty_unregister_driver(struct tty_driver *driver)
>  	if (!ent)
>  		return;
>  		
> -	remove_proc_entry(driver->driver_name, proc_tty_driver);
> +	remove_proc_entry(ent->name, proc_tty_driver);

Yes, that makes sense. Using possibly stale driver_name cannot really
work out. I only wonder why nobody noticed until now...

So, can you reproduce also on 4.13 or something newer like that?

thanks,
-- 
js
suse labs