linux-kernel - Re: Bug report - slab-out-of-bounds in vcs_scr

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Message-ID: <nycvar.YSQ.7.76.1911261652290.8537@knanqh.ubzr>
Date:   Tue, 26 Nov 2019 16:55:32 -0500 (EST)
From:   Nicolas Pitre <nico@...xnic.net>
To:     Greg KH <gregkh@...uxfoundation.org>
cc:     Jiri Slaby <jslaby@...e.com>,
        Or Cohen <orcohen@...oaltonetworks.com>, textshell@...uujin.de,
        Daniel Vetter <daniel.vetter@...ll.ch>, sam@...nborg.org,
        mpatocka@...hat.com, ghalat@...hat.com,
        linux-kernel@...r.kernel.org, jwilk@...lk.net,
        Nadav Markus <nmarkus@...oaltonetworks.com>,
        syzkaller@...glegroups.com
Subject: Re: Bug report - slab-out-of-bounds in vcs_scr_readw

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@...libre.com>
> Cc: <stable@...r.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;
> 
>