fs/compat_ioctl.c: VIDEO_SET_SPU_PALETTE missing error check

The compat ioctl for VIDEO_SET_SPU_PALETTE was missing an error check
while converting ioctl arguments.  This could lead to leaking kernel
stack contents into userspace.

Patch extracted from existing fix in grsecurity.

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: David Miller <davem@davemloft.net>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: PaX Team <pageexec@freemail.hu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
static int ppp_gidle(unsigned int fd, unsigned int cmd,
		struct ppp_idle32 __user *idle32)
{
	struct ppp_idle __user *idle;
	__kernel_time_t xmit, recv;
	int err;

	idle = compat_alloc_user_space(sizeof(*idle));

	err = sys_ioctl(fd, PPPIOCGIDLE, (unsigned long) idle);

	if (!err) {
		if (get_user(xmit, &idle->xmit_idle) ||
		    get_user(recv, &idle->recv_idle) ||
		    put_user(xmit, &idle32->xmit_idle) ||
		    put_user(recv, &idle32->recv_idle))
			err = -EFAULT;
	}
	return err;
}

static int ppp_gidle(unsigned int fd, unsigned int cmd,
		struct ppp_idle32 __user *idle32)
{
	struct ppp_idle __user *idle;
	__kernel_time_t xmit, recv;
	int err;

	idle = compat_alloc_user_space(sizeof(*idle));

	err = sys_ioctl(fd, PPPIOCGIDLE, (unsigned long) idle);

	if (!err) {
		if (get_user(xmit, &idle->xmit_idle) ||
		    get_user(recv, &idle->recv_idle) ||
		    put_user(xmit, &idle32->xmit_idle) ||
		    put_user(recv, &idle32->recv_idle))
			err = -EFAULT;
	}
	return err;
}
