1 files changed, 129 insertions, 0 deletions

diff --git a/tools/testing/selftests/proc/setns-dcache.c b/tools/testing/selftests/proc/setns-dcache.c
new file mode 100644
index 000000000000..60ab197a73fc
--- /dev/null
+++ b/tools/testing/selftests/proc/setns-dcache.c
@@ -0,0 +1,129 @@
+/*
+ * Copyright © 2019 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * Test that setns(CLONE_NEWNET) points to new /proc/net content even
+ * if old one is in dcache.
+ *
+ * FIXME /proc/net/unix is under CONFIG_UNIX which can be disabled.
+ */
+#undef NDEBUG
+#include <assert.h>
+#include <errno.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/socket.h>
+
+static pid_t pid = -1;
+
+static void f(void)
+{
+        if (pid > 0) {
+                kill(pid, SIGTERM);
+        }
+}
+
+int main(void)
+{
+        int fd[2];
+        char _ = 0;
+        int nsfd;
+
+        atexit(f);
+
+        /* Check for priviledges and syscall availability straight away. */
+        if (unshare(CLONE_NEWNET) == -1) {
+                if (errno == ENOSYS || errno == EPERM) {
+                        return 4;
+                }
+                return 1;
+        }
+        /* Distinguisher between two otherwise empty net namespaces. */
+        if (socket(AF_UNIX, SOCK_STREAM, 0) == -1) {
+                return 1;
+        }
+
+        if (pipe(fd) == -1) {
+                return 1;
+        }
+
+        pid = fork();
+        if (pid == -1) {
+                return 1;
+        }
+
+        if (pid == 0) {
+                if (unshare(CLONE_NEWNET) == -1) {
+                        return 1;
+                }
+
+                if (write(fd[1], &_, 1) != 1) {
+                        return 1;
+                }
+
+                pause();
+
+                return 0;
+        }
+
+        if (read(fd[0], &_, 1) != 1) {
+                return 1;
+        }
+
+        {
+                char buf[64];
+                snprintf(buf, sizeof(buf), "/proc/%u/ns/net", pid);
+                nsfd = open(buf, O_RDONLY);
+                if (nsfd == -1) {
+                        return 1;
+                }
+        }
+
+        /* Reliably pin dentry into dcache. */
+        (void)open("/proc/net/unix", O_RDONLY);
+
+        if (setns(nsfd, CLONE_NEWNET) == -1) {
+                return 1;
+        }
+
+        kill(pid, SIGTERM);
+        pid = 0;
+
+        {
+                char buf[4096];
+                ssize_t rv;
+                int fd;
+
+                fd = open("/proc/net/unix", O_RDONLY);
+                if (fd == -1) {
+                        return 1;
+                }
+
+#define S "Num       RefCount Protocol Flags    Type St Inode Path\n"
+                rv = read(fd, buf, sizeof(buf));
+
+                assert(rv == strlen(S));
+                assert(memcmp(buf, S, strlen(S)) == 0);
+        }
+
+        return 0;
+}