[IA64] SN2: security hole in sn2_ptc_proc_write

Security hole in sn2_ptc_proc_write

It is possible to overrun a buffer with a write to this /proc file.
Signed-off-by: NCliff Wickman <cpw@sgi.com>
Signed-off-by: NTony Luck <tony.luck@intel.com>

arch/ia64/sn/kernel/sn2/sn2_smp.c

@@ -512,6 +512,8 @@ static ssize_t sn2_ptc_proc_write(struct file *file, const char __user *user, si
 	int cpu;
 	char optstr[64];
 
+	if (count > sizeof(optstr))
+		return -EINVAL;
 	if (copy_from_user(optstr, user, count))
 		return -EFAULT;
 	optstr[count - 1] = '\0';