tests: verify the auxstr of setns(2) when --namespace=switch is given

Signed-off-by: Masatake YAMATO <[email protected]>

Author: masatake

tests/gen_tests.in

@@ -985,6 +985,7 @@ setgroups	-s2 -a17
 setgroups32	-s2 -a19
 sethostname	-a22
 setns	-a21
+setns-report-ns-id	-a11	-e trace=setns -e namespace=switch -e signal=none
 setregid	-a15
 setregid32	-a17
 setresgid	-a19

tests/pure_executables.list

@@ -716,6 +716,7 @@ setgroups
 setgroups32
 sethostname
 setns
+setns-report-ns-id
 setregid
 setregid32
 setresgid

tests/setns-report-ns-id.c

@@ -0,0 +1,121 @@
+/*
+ * Check appending auxstr of setns(2) when --namespace=switch is given
+ *
+ * Copyright (c) 2024 The strace developers.
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "tests.h"
+#include "scno.h"
+#include "xmalloc.h"
+
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <signal.h>
+#include <sys/wait.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/socket.h>
+
+typedef struct msg {
+	enum {
+		MSG_OK = 0,
+		MSG_ERR_CLOSE,
+		MSG_ERR_UNSHARE,
+	} type;
+	int err;
+} msg_t;
+
+int
+main(void)
+{
+	int sv[2];
+	if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv) < 0)
+		perror_msg_and_skip("pipe");
+
+	pid_t pid = fork();
+	if (pid == 0) {
+		msg_t msg;
+		char c;
+
+		if (syscall(__NR_unshare, 0x10000000) < 0) {
+			msg.type = MSG_ERR_UNSHARE;
+			msg.err = errno;
+			write(sv[1], &msg, sizeof(msg));
+			return 1;
+		}
+
+		msg.type = MSG_OK;
+		write(sv[1], &msg, sizeof(msg));
+		read(sv[1], &c, 1);
+	} else if (pid > 0) {
+		ssize_t r;
+		msg_t msg;
+
+		r = read(sv[0], &msg, sizeof(msg));
+		if (r < 0)
+			perror_msg_and_skip("read");
+		if (r == 0)
+			error_msg_and_skip("unexpected EOF");
+		else if (r != sizeof(msg))
+			error_msg_and_skip("data from the child it too short");
+
+		if (msg.type != MSG_OK) {
+			errno = msg.err;
+			perror_msg_and_skip("%s",
+					    (msg.type == MSG_ERR_CLOSE)? "close":
+					    (msg.type == MSG_ERR_UNSHARE)? "unshare":
+					    "unknown");
+		}
+
+		char *ns_path = xasprintf("/proc/%u/ns/user", pid);
+		int ns_fd = open(ns_path, O_RDONLY);
+		if (ns_fd < 0) {
+			int e = errno;
+			write(sv[0], (char[]){'\n'}, 1);
+			wait(NULL);
+			errno = e;
+			perror_msg_and_skip("open");
+		}
+
+		long rc = syscall(__NR_setns, ns_fd, 0x10000000);
+		printf("setns(%d, CLONE_NEWUSER) = %s%s",
+		       ns_fd, sprintrc(rc), rc == 0? "": "\n");
+
+		if (rc == 0) {
+			char buf[PATH_MAX + 1];
+			int n  = readlink(ns_path, buf, sizeof(buf));
+			if (n < 0) {
+				int e = errno;
+				write(sv[0], (char[]){'\n'}, 1);
+				wait(NULL);
+				errno = e;
+				perror_msg_and_skip("readlink");
+			}
+			else if ((size_t)n >= sizeof(buf)) {
+				write(sv[0], (char[]){'\n'}, 1);
+				wait(NULL);
+				error_msg_and_skip("too large readlink result");
+			}
+			buf[n] = '\0';
+			printf(" (%s)\n", buf);
+		}
+
+		write(sv[0], (char[]){'\n'}, 1);
+		wait(NULL);
+
+		/* Verify that strace doen't print a namespace when an error occurs. */
+		rc = syscall(__NR_setns, -1, 0x10000000);
+		printf("setns(-1, CLONE_NEWUSER) = %s\n", sprintrc(rc));
+
+		puts("+++ exited with 0 +++");
+
+	} else
+		perror_msg_and_skip("fork");
+
+	return 0;
+}