Re: Bug report - slab-out-of-bounds in vcs_scr_readw

From: Nicolas Pitre <nico@fluxnic.net>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>,
	Or Cohen <orcohen@paloaltonetworks.com>,
	textshell@uchuujin.de, Daniel Vetter <daniel.vetter@ffwll.ch>,
	sam@ravnborg.org, mpatocka@redhat.com, ghalat@redhat.com,
	linux-kernel@vger.kernel.org, jwilk@jwilk.net,
	Nadav Markus <nmarkus@paloaltonetworks.com>,
	syzkaller@googlegroups.com
Subject: Re: Bug report - slab-out-of-bounds in vcs_scr_readw
Date: Tue, 26 Nov 2019 16:55:32 -0500 (EST)	[thread overview]
Message-ID: <nycvar.YSQ.7.76.1911261652290.8537@knanqh.ubzr> (raw)
In-Reply-To: <nycvar.YSQ.7.76.1911051030580.30289@knanqh.ubzr>

Greg, could you apply this please?

On Tue, 5 Nov 2019, Nicolas Pitre wrote:

> Subject: [PATCH] vcs: prevent write access to vcsu devices
> 
> Commit d21b0be246bf ("vt: introduce unicode mode for /dev/vcs") guarded
> against using devices containing attributes as this is not yet
> implemented. It however failed to guard against writes to any devices
> as this is also unimplemented.
> 
> Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
> Cc: <stable@vger.kernel.org> # v4.19+
> 
> diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
> index fa07d79027..ef19b95b73 100644
> --- a/drivers/tty/vt/vc_screen.c
> +++ b/drivers/tty/vt/vc_screen.c
> @@ -456,6 +456,9 @@ vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
>  	size_t ret;
>  	char *con_buf;
>  
> +	if (use_unicode(inode))
> +		return -EOPNOTSUPP;
> +
>  	con_buf = (char *) __get_free_page(GFP_KERNEL);
>  	if (!con_buf)
>  		return -ENOMEM;
> 
> 