selftests: proc: test subset=pid

Test that /proc instance mounted with

	mount -t proc -o subset=pid

contains only ".", "..", "self", "thread-self" and pid directories.

Note:
Currently "subset=pid" doesn't return "." and ".." via readdir.
This must be a bug.

Link: https://lkml.kernel.org/r/YFYZZ7WGaZlsnChS@localhost.localdomain
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Alexey Gladkov <gladkov.alexey@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/tools/testing/selftests/proc/Makefile b/tools/testing/selftests/proc/Makefile
index 8be8a03..1054e40 100644 (file)
--- a/tools/testing/selftests/proc/Makefile
+++ b/tools/testing/selftests/proc/Makefile
@@ -12,6 +12,7 @@ TEST_GEN_PROGS += proc-self-map-files-001
 TEST_GEN_PROGS += proc-self-map-files-002
 TEST_GEN_PROGS += proc-self-syscall
 TEST_GEN_PROGS += proc-self-wchan
+TEST_GEN_PROGS += proc-subset-pid
 TEST_GEN_PROGS += proc-uptime-001
 TEST_GEN_PROGS += proc-uptime-002
 TEST_GEN_PROGS += read

diff --git a/tools/testing/selftests/proc/proc-subset-pid.c b/tools/testing/selftests/proc/proc-subset-pid.c
new file mode 100644 (file)
index 0000000..d1052bc
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-subset-pid.c
@@ -0,0 +1,121 @@
+/*
+ * Copyright (c) 2021 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 "mount -t proc -o subset=pid" hides everything but pids,
+ * /proc/self and /proc/thread-self.
+ */
+#undef NDEBUG
+#include <assert.h>
+#include <errno.h>
+#include <sched.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <dirent.h>
+#include <unistd.h>
+#include <stdio.h>
+
+static inline bool streq(const char *a, const char *b)
+{
+       return strcmp(a, b) == 0;
+}
+
+static void make_private_proc(void)
+{
+       if (unshare(CLONE_NEWNS) == -1) {
+               if (errno == ENOSYS || errno == EPERM) {
+                       exit(4);
+               }
+               exit(1);
+       }
+       if (mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL) == -1) {
+               exit(1);
+       }
+       if (mount(NULL, "/proc", "proc", 0, "subset=pid") == -1) {
+               exit(1);
+       }
+}
+
+static bool string_is_pid(const char *s)
+{
+       while (1) {
+               switch (*s++) {
+               case '0':case '1':case '2':case '3':case '4':
+               case '5':case '6':case '7':case '8':case '9':
+                       continue;
+
+               case '\0':
+                       return true;
+
+               default:
+                       return false;
+               }
+       }
+}
+
+int main(void)
+{
+       make_private_proc();
+
+       DIR *d = opendir("/proc");
+       assert(d);
+
+       struct dirent *de;
+
+       bool dot = false;
+       bool dot_dot = false;
+       bool self = false;
+       bool thread_self = false;
+
+       while ((de = readdir(d))) {
+               if (streq(de->d_name, ".")) {
+                       assert(!dot);
+                       dot = true;
+                       assert(de->d_type == DT_DIR);
+               } else if (streq(de->d_name, "..")) {
+                       assert(!dot_dot);
+                       dot_dot = true;
+                       assert(de->d_type == DT_DIR);
+               } else if (streq(de->d_name, "self")) {
+                       assert(!self);
+                       self = true;
+                       assert(de->d_type == DT_LNK);
+               } else if (streq(de->d_name, "thread-self")) {
+                       assert(!thread_self);
+                       thread_self = true;
+                       assert(de->d_type == DT_LNK);
+               } else {
+                       if (!string_is_pid(de->d_name)) {
+                               fprintf(stderr, "d_name '%s'\n", de->d_name);
+                               assert(0);
+                       }
+                       assert(de->d_type == DT_DIR);
+               }
+       }
+
+       char c;
+       int rv = readlink("/proc/cpuinfo", &c, 1);
+       assert(rv == -1 && errno == ENOENT);
+
+       int fd = open("/proc/cpuinfo", O_RDONLY);
+       assert(fd == -1 && errno == ENOENT);
+
+       return 0;
+}