s390/ptrace: fix PSW mask check

The PSW mask check of the PTRACE_POKEUSR_AREA command is incorrect.
The PSW_MASK_USER define contains the PSW_MASK_ASC bits, the ptrace
interface accepts all combinations for the address-space-control
bits. To protect the kernel space the PSW mask check in ptrace needs
to reject the address-space-control bit combination for home space.

Fixes CVE-2014-3534

Cc: stable@vger.kernel.org
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
static int s390_regs_get(struct task_struct *target,
			 const struct user_regset *regset,
			 unsigned int pos, unsigned int count,
			 void *kbuf, void __user *ubuf)
{
	if (target == current)
		save_access_regs(target->thread.acrs);

	if (kbuf) {
		unsigned long *k = kbuf;
		while (count > 0) {
			*k++ = __peek_user(target, pos);
			count -= sizeof(*k);
			pos += sizeof(*k);
		}
	} else {
		unsigned long __user *u = ubuf;
		while (count > 0) {
			if (__put_user(__peek_user(target, pos), u++))
				return -EFAULT;
			count -= sizeof(*u);
			pos += sizeof(*u);
		}
	}
	return 0;
}

static int s390_regs_get(struct task_struct *target,
			 const struct user_regset *regset,
			 unsigned int pos, unsigned int count,
			 void *kbuf, void __user *ubuf)
{
	if (target == current)
		save_access_regs(target->thread.acrs);

	if (kbuf) {
		unsigned long *k = kbuf;
		while (count > 0) {
			*k++ = __peek_user(target, pos);
			count -= sizeof(*k);
			pos += sizeof(*k);
		}
	} else {
		unsigned long __user *u = ubuf;
		while (count > 0) {
			if (__put_user(__peek_user(target, pos), u++))
				return -EFAULT;
			count -= sizeof(*u);
			pos += sizeof(*u);
		}
	}
	return 0;
}
