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Subject: Re: [PATCH] tty: fix compat TIOCGSERIAL leaking uninitialized memory
To:     Eric Biggers <ebiggers@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        Al Viro <viro@zeniv.linux.org.uk>
References: <000000000000387920059f4e0351@google.com>
 <20200224083838.306381-1-ebiggers@kernel.org>
From:   Jiri Slaby <jslaby@suse.com>
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Message-ID: <1edbbced-58c1-7674-2d01-6a807ddf5968@suse.com>
Date:   Mon, 24 Feb 2020 09:47:26 +0100
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On 24. 02. 20, 9:38, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Commit 77654350306a ("take compat TIOC[SG]SERIAL treatment into
> tty_compat_ioctl()") changed the compat version of TIOCGSERIAL to start
> copying a whole struct 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.
> 
> Reported-by: syzbot+8da9175e28eadcb203ce@syzkaller.appspotmail.com
> Fixes: 77654350306a ("take compat TIOC[SG]SERIAL treatment into tty_compat_ioctl()")
> Cc: <stable@vger.kernel.org> # v4.20+
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  drivers/tty/tty_io.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 1fcf7ad83dfa0..d24c250312edf 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -2731,6 +2731,7 @@ static int compat_tty_tiocgserial(struct tty_struct *tty,
>  	struct serial_struct v;
>  	int err;
>  	memset(&v, 0, sizeof(struct serial_struct));
> +	memset(&v32, 0, sizeof(struct serial_struct32));

sizeof(v32) please.

thanks,
-- 
js
suse labs