pidfd: Replace open-coded receive_fd()

Replace the open-coded version of receive_fd() with a call to the
new helper.

Thanks to Vamshi K Sthambamkadi <[email protected]> for
catching a missed fput() in an earlier version of this patch.

Cc: Christoph Hellwig <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: [email protected]
Cc: [email protected]
Reviewed-by: Sargun Dhillon <[email protected]>
Acked-by: Christian Brauner <[email protected]>
Signed-off-by: Kees Cook <[email protected]>

Author: kees

kernel/pid.c

@@ -636,19 +636,8 @@ static int pidfd_getfd(struct pid *pid, int fd)
 	if (IS_ERR(file))
 		return PTR_ERR(file);
 
-	ret = security_file_receive(file);
-	if (ret) {
-		fput(file);
-		return ret;
-	}
-
-	ret = get_unused_fd_flags(O_CLOEXEC);
-	if (ret < 0) {
-		fput(file);
-	} else {
-		__receive_sock(file);
-		fd_install(ret, file);
-	}
+	ret = receive_fd(file, O_CLOEXEC);
+	fput(file);
 
 	return ret;
 }