Re: [PATCH] tty: fix compat TIOCGSERIAL leaking uninitialized memory

[Jiri Slaby]

On 24. 02. 20, 9:38, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 77654350306a ("take compat TIOC[SG]SERIAL treatment into tty_compat_ioctl()")
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.20+
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> ---
>  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