ARM: 9111/1: oabi-compat: rework fcntl64() emulation

This is one of the last users of get_fs(), and this is fairly easy to
change, since the infrastructure for it is already there.

The replacement here is essentially a copy of the existing fcntl64()
syscall entry function.
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

arch/arm/kernel/sys_oabi-compat.c

@@ -194,56 +194,83 @@ struct oabi_flock64 {
 	pid_t	l_pid;
 } __attribute__ ((packed,aligned(4)));
 
-static long do_locks(unsigned int fd, unsigned int cmd,
-				 unsigned long arg)
+static int get_oabi_flock(struct flock64 *kernel, struct oabi_flock64 __user *arg)
 {
-	struct flock64 kernel;
 	struct oabi_flock64 user;
-	mm_segment_t fs;
-	long ret;
 
 	if (copy_from_user(&user, (struct oabi_flock64 __user *)arg,
 			   sizeof(user)))
 		return -EFAULT;
-	kernel.l_type	= user.l_type;
-	kernel.l_whence	= user.l_whence;
-	kernel.l_start	= user.l_start;
-	kernel.l_len	= user.l_len;
-	kernel.l_pid	= user.l_pid;
-
-	fs = get_fs();
-	set_fs(KERNEL_DS);
-	ret = sys_fcntl64(fd, cmd, (unsigned long)&kernel);
-	set_fs(fs);
-
-	if (!ret && (cmd == F_GETLK64 || cmd == F_OFD_GETLK)) {
-		user.l_type	= kernel.l_type;
-		user.l_whence	= kernel.l_whence;
-		user.l_start	= kernel.l_start;
-		user.l_len	= kernel.l_len;
-		user.l_pid	= kernel.l_pid;
-		if (copy_to_user((struct oabi_flock64 __user *)arg,
-				 &user, sizeof(user)))
-			ret = -EFAULT;
-	}
-	return ret;
+
+	kernel->l_type	 = user.l_type;
+	kernel->l_whence = user.l_whence;
+	kernel->l_start	 = user.l_start;
+	kernel->l_len	 = user.l_len;
+	kernel->l_pid	 = user.l_pid;
+
+	return 0;
+}
+
+static int put_oabi_flock(struct flock64 *kernel, struct oabi_flock64 __user *arg)
+{
+	struct oabi_flock64 user;
+
+	user.l_type	= kernel->l_type;
+	user.l_whence	= kernel->l_whence;
+	user.l_start	= kernel->l_start;
+	user.l_len	= kernel->l_len;
+	user.l_pid	= kernel->l_pid;
+
+	if (copy_to_user((struct oabi_flock64 __user *)arg,
+			 &user, sizeof(user)))
+		return -EFAULT;
+
+	return 0;
 }
 
 asmlinkage long sys_oabi_fcntl64(unsigned int fd, unsigned int cmd,
 				 unsigned long arg)
 {
+	void __user *argp = (void __user *)arg;
+	struct fd f = fdget_raw(fd);
+	struct flock64 flock;
+	long err = -EBADF;
+
+	if (!f.file)
+		goto out;
+
 	switch (cmd) {
-	case F_OFD_GETLK:
-	case F_OFD_SETLK:
-	case F_OFD_SETLKW:
 	case F_GETLK64:
+	case F_OFD_GETLK:
+		err = security_file_fcntl(f.file, cmd, arg);
+		if (err)
+			break;
+		err = get_oabi_flock(&flock, argp);
+		if (err)
+			break;
+		err = fcntl_getlk64(f.file, cmd, &flock);
+		if (!err)
+		       err = put_oabi_flock(&flock, argp);
+		break;
 	case F_SETLK64:
 	case F_SETLKW64:
-		return do_locks(fd, cmd, arg);
-
+	case F_OFD_SETLK:
+	case F_OFD_SETLKW:
+		err = security_file_fcntl(f.file, cmd, arg);
+		if (err)
+			break;
+		err = get_oabi_flock(&flock, argp);
+		if (err)
+			break;
+		err = fcntl_setlk64(fd, f.file, cmd, &flock);
+		break;
 	default:
-		return sys_fcntl64(fd, cmd, arg);
+		err = sys_fcntl64(fd, cmd, arg);
+		break;
 	}
+	fdput(f);
+out:
+	return err;
 }
 
 struct oabi_epoll_event {