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 do_video_set_spu_palette(unsigned int fd, unsigned int cmd,
		struct compat_video_spu_palette __user *up)
{
	struct video_spu_palette __user *up_native;
	compat_uptr_t palp;
	int length, err;
 
 	err  = get_user(palp, &up->palette);
 	err |= get_user(length, &up->length);
	if (err)
		return -EFAULT;
 
 	up_native = compat_alloc_user_space(sizeof(struct video_spu_palette));
 	err  = put_user(compat_ptr(palp), &up_native->palette);
	err |= put_user(length, &up_native->length);
	if (err)
		return -EFAULT;

	err = sys_ioctl(fd, cmd, (unsigned long) up_native);

	return err;
}

static int do_video_set_spu_palette(unsigned int fd, unsigned int cmd,
		struct compat_video_spu_palette __user *up)
{
	struct video_spu_palette __user *up_native;
	compat_uptr_t palp;
	int length, err;
 
 	err  = get_user(palp, &up->palette);
 	err |= get_user(length, &up->length);
 
 	up_native = compat_alloc_user_space(sizeof(struct video_spu_palette));
 	err  = put_user(compat_ptr(palp), &up_native->palette);
	err |= put_user(length, &up_native->length);
	if (err)
		return -EFAULT;

	err = sys_ioctl(fd, cmd, (unsigned long) up_native);

	return err;
}
