Fix sys_ipc() SEMCTL on sparc64.

changeset 6536a6b331d3225921c398eb7c6e4ecedb9b05e0 from mainline

Thanks to Tom Callaway for the excellent bug report and
test case.

sys_ipc() has several problems, most to due with semaphore
call handling:

1) 'err' return should be a 'long'
2) "union semun" is passed in a register on 64-bit compared
   to 32-bit which provides it on the stack and therefore
   by reference
3) Second and third arguments to SEMCTL are swapped compared
   to 32-bit.
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

arch/sparc64/kernel/sys_sparc.c

@@ -436,7 +436,7 @@ asmlinkage long sparc_pipe(struct pt_regs *regs)
 asmlinkage long sys_ipc(unsigned int call, int first, unsigned long second,
 			unsigned long third, void __user *ptr, long fifth)
 {
-	int err;
+	long err;
 
 	/* No need for backward compatibility. We can start fresh... */
 	if (call <= SEMCTL) {
@@ -453,16 +453,9 @@ asmlinkage long sys_ipc(unsigned int call, int first, unsigned long second,
 			err = sys_semget(first, (int)second, (int)third);
 			goto out;
 		case SEMCTL: {
-			union semun fourth;
-			err = -EINVAL;
-			if (!ptr)
-				goto out;
-			err = -EFAULT;
-			if (get_user(fourth.__pad,
-				     (void __user * __user *) ptr))
-				goto out;
-			err = sys_semctl(first, (int)second | IPC_64,
-					 (int)third, fourth);
+			err = sys_semctl(first, third,
+					 (int)second | IPC_64,
+					 (union semun) ptr);
 			goto out;
 		}
 		default: