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>
unsigned long regs_get_register(struct pt_regs *regs, unsigned int offset)
{
	if (offset >= NUM_GPRS)
		return 0;
	return regs->gprs[offset];
}

unsigned long regs_get_register(struct pt_regs *regs, unsigned int offset)
{
	if (offset >= NUM_GPRS)
		return 0;
	return regs->gprs[offset];
}
