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_system_call_get(struct task_struct *target,
				const struct user_regset *regset,
				unsigned int pos, unsigned int count,
				void *kbuf, void __user *ubuf)
{
	unsigned int *data = &task_thread_info(target)->system_call;
	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
				   data, 0, sizeof(unsigned int));
}

static int s390_system_call_get(struct task_struct *target,
				const struct user_regset *regset,
				unsigned int pos, unsigned int count,
				void *kbuf, void __user *ubuf)
{
	unsigned int *data = &task_thread_info(target)->system_call;
	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
				   data, 0, sizeof(unsigned int));
}
