linux-kernel - Re: [PATCH v2 1/2] tty: fix compat TIOCGSERIAL leaking uninitialized memory

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Date:   Tue, 25 Feb 2020 08:30:35 +0100
From:   Jiri Slaby <jslaby@...e.com>
To:     Eric Biggers <ebiggers@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v2 1/2] tty: fix compat TIOCGSERIAL leaking uninitialized
 memory

On 24. 02. 20, 19:20, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> Commit 77654350306a ("take compat TIOC[SG]SERIAL treatment into
> tty_compat_ioctl()") changed the compat version of TIOCGSERIAL to start
> copying a whole 'serial_struct32' to userspace rather than individual
> fields, but failed to initialize all padding and fields -- namely the
> hole after the 'iomem_reg_shift' field, and the 'reserved' field.
> 
> Fix this by initializing the struct to zero.
> 
> [v2: use sizeof, and convert the adjacent line for consistency.]
> 
> Reported-by: syzbot+8da9175e28eadcb203ce@...kaller.appspotmail.com
> Fixes: 77654350306a ("take compat TIOC[SG]SERIAL treatment into tty_compat_ioctl()")
> Cc: <stable@...r.kernel.org> # v4.20+
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

Acked-by: Jiri Slaby <jslaby@...e.cz>

> ---
>  drivers/tty/tty_io.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 1fcf7ad83dfa0a..db4a13bc855ed6 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -2730,7 +2730,9 @@ static int compat_tty_tiocgserial(struct tty_struct *tty,
>  	struct serial_struct32 v32;
>  	struct serial_struct v;
>  	int err;
> -	memset(&v, 0, sizeof(struct serial_struct));
> +
> +	memset(&v, 0, sizeof(v));
> +	memset(&v32, 0, sizeof(v32));
>  
>  	if (!tty->ops->set_serial)
>  		return -ENOTTY;
> 


-- 
js
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