linux-kernel - Re: [PATCH] tty_io: Fix a missing-check bug in drivers/tty/tty

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 22 May 2019 06:25:36 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     Gen Zhang <blackgod016574@...il.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty_io: Fix a missing-check bug in drivers/tty/tty_io.c

On 22. 05. 19, 3:40, Gen Zhang wrote:
> In alloc_tty_struct(), tty->dev is assigned by tty_get_device(). And it
> calls class_find_device(). And class_find_device() may return NULL.
> And tty->dev is dereferenced in the following codes. When 
> tty_get_device() returns NULL, dereferencing this tty->dev null pointer
> may cause the kernel go wrong. Thus we should check tty->dev.
> Further, if tty_get_device() returns NULL, we should free tty and 
> return NULL.
> 
> Signed-off-by: Gen Zhang <blackgod016574@...il.com>
> 
> ---
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 033ac7e..1444b59 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -3008,6 +3008,10 @@ struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
>  	tty->index = idx;
>  	tty_line_name(driver, idx, tty->name);
>  	tty->dev = tty_get_device(tty);
> +	if (!tty->dev) {
> +		kfree(tty);
> +		return NULL;
> +	}

This is incorrect, you introduced an ldisc reference leak.

And can this happen at all?

thanks,
-- 
js
suse labs