On 10/10/24 12:15, Lorenzo Stoakes wrote:
Add tests to assert that PIDFD_SELF_* correctly refers to the current
thread and process.

This is only practically meaningful to pidfd_send_signal() and
pidfd_getfd(), but also explicitly test that we disallow this feature for
setns() where it would make no sense.

We cannot reasonably wait on ourself using waitid(P_PIDFD, ...) so while in
theory PIDFD_SELF_* would work here, we'd be left blocked if we tried it.

We defer testing of mm-specific functionality which uses pidfd, namely
process_madvise() and process_mrelease() to mm testing (though note the
latter can not be sensibly tested as it would require the testing process
to be dying).

Signed-off-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>
---
  tools/testing/selftests/pidfd/pidfd.h         |   8 ++
  .../selftests/pidfd/pidfd_getfd_test.c        | 136 ++++++++++++++++++
  .../selftests/pidfd/pidfd_setns_test.c        |  11 ++
  tools/testing/selftests/pidfd/pidfd_test.c    |  67 +++++++--
  4 files changed, 213 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/pidfd/pidfd.h 
b/tools/testing/selftests/pidfd/pidfd.h
index 88d6830ee004..1640b711889b 100644
--- a/tools/testing/selftests/pidfd/pidfd.h
+++ b/tools/testing/selftests/pidfd/pidfd.h
@@ -50,6 +50,14 @@
  #define PIDFD_NONBLOCK O_NONBLOCK
  #endif
+/* System header file may not have this available. */
+#ifndef PIDFD_SELF_THREAD
+#define PIDFD_SELF_THREAD -100
+#endif
+#ifndef PIDFD_SELF_THREAD_GROUP
+#define PIDFD_SELF_THREAD_GROUP -200
+#endif
+

Can't we pick these up from linux/pidfd.h - patch 2/3 adds
them.

  /*
   * The kernel reserves 300 pids via RESERVED_PIDS in kernel/pid.c
   * That means, when it wraps around any pid < 300 will be skipped.
diff --git a/tools/testing/selftests/pidfd/pidfd_getfd_test.c 
b/tools/testing/selftests/pidfd/pidfd_getfd_test.c
index cd51d547b751..10793fc845ed 100644
--- a/tools/testing/selftests/pidfd/pidfd_getfd_test.c
+++ b/tools/testing/selftests/pidfd/pidfd_getfd_test.c
@@ -6,6 +6,7 @@
  #include <limits.h>
  #include <linux/types.h>
  #include <poll.h>
+#include <pthread.h>
  #include <sched.h>
  #include <signal.h>
  #include <stdio.h>
@@ -15,6 +16,7 @@
  #include <sys/prctl.h>
  #include <sys/wait.h>
  #include <unistd.h>
+#include <sys/mman.h>
  #include <sys/socket.h>
  #include <linux/kcmp.h>
@@ -114,6 +116,89 @@ static int child(int sk)
        return ret;
  }
+static int __pidfd_self_thread_worker(unsigned long page_size)
+{
+       int memfd;
+       int newfd;
+       char *ptr;
+       int ret = 0;
+
+       /*
+        * Unshare our FDs so we have our own set. This means
+        * PIDFD_SELF_THREAD_GROUP will fail.
+        */
+       if (unshare(CLONE_FILES) < 0) {
+               ret = -errno;
+               goto exit;
+       }
+
+       /* Truncate, map in and write to our memfd. */
+       memfd = sys_memfd_create("test_self_child", 0);

Missing eror check.

+       if (ftruncate(memfd, page_size)) {
+               ret = -errno;
+               goto exit;

Hmm. you probably need scoped cleanup paths. "exit" closes
memfd and newfd which isn't open yet and sys_memfd_create()
could fail and memfd doesn't need closing?

+       }
+
+       ptr = mmap(NULL, page_size, PROT_READ | PROT_WRITE,
+                  MAP_SHARED, memfd, 0);
+       if (ptr == MAP_FAILED) {
+               ret = -errno;
+               goto exit;
+       }
+       ptr[0] = 'y';
+       if (munmap(ptr, page_size)) {
+               ret = -errno;
+               goto exit;
+       }
+
+       /* Get a thread-local duplicate of our memfd. */
+       newfd = sys_pidfd_getfd(PIDFD_SELF_THREAD, memfd, 0);
+       if (newfd < 0) {
+               ret = -errno;
+               goto exit;

Same comment here - "exit" closes newfd

+       }
+
+       if (memfd == newfd) {
+               ret = -EINVAL;
+               goto exit;
+       }
+
+       /* Map in new fd and make sure that the data is as expected. */
+       ptr = mmap(NULL, page_size, PROT_READ | PROT_WRITE,
+                  MAP_SHARED, newfd, 0);
+       if (ptr == MAP_FAILED) {
+               ret = -errno;
+               goto exit;
+       }
+
+       if (ptr[0] != 'y') {
+               ret = -EINVAL;
+               goto exit;
+       }
+
+       if (munmap(ptr, page_size)) {
+               ret = -errno;
+               goto exit;
+       }
+
+exit:
+       /* Cleanup. */
+       close(newfd);
+       close(memfd);
+
+       return ret;
+}
+
+static void *pidfd_self_thread_worker(void *arg)
+{
+       unsigned long page_size = (unsigned long)arg;
+       int ret;
+
+       ret = __pidfd_self_thread_worker(page_size);

Don't you want to check error here?

+
+       return (void *)(intptr_t)ret;
+}
+
  FIXTURE(child)
  {
        /*
@@ -264,6 +349,57 @@ TEST_F(child, no_strange_EBADF)
        EXPECT_EQ(errno, ESRCH);
  }
+TEST(pidfd_self)
+{
+       int memfd = sys_memfd_create("test_self", 0);
+       unsigned long page_size = sysconf(_SC_PAGESIZE);
+       int newfd;
+       char *ptr;
+       pthread_t thread;
+       void *res;
+       int err;
+
+       ASSERT_GE(memfd, 0);
+       ASSERT_EQ(ftruncate(memfd, page_size), 0);
+
+       /*
+        * Map so we can assert that the duplicated fd references the same
+        * memory.
+        */
+       ptr = mmap(NULL, page_size, PROT_READ | PROT_WRITE,
+                  MAP_SHARED, memfd, 0);
+       ASSERT_NE(ptr, MAP_FAILED);
+       ptr[0] = 'x';
+       ASSERT_EQ(munmap(ptr, page_size), 0);
+
+       /* Now get a duplicate of our memfd. */
+       newfd = sys_pidfd_getfd(PIDFD_SELF_THREAD_GROUP, memfd, 0);
+       ASSERT_GE(newfd, 0);
+       ASSERT_NE(memfd, newfd);
+
+       /* Now map duplicate fd and make sure it references the same memory. */
+       ptr = mmap(NULL, page_size, PROT_READ | PROT_WRITE,
+                  MAP_SHARED, newfd, 0);
+       ASSERT_NE(ptr, MAP_FAILED);
+       ASSERT_EQ(ptr[0], 'x');
+       ASSERT_EQ(munmap(ptr, page_size), 0);
+
+       /* Cleanup. */
+       close(memfd);
+       close(newfd);
+
+       /*
+        * Fire up the thread and assert that we can lookup the thread-specific
+        * PIDFD_SELF_THREAD (also aliased by PIDFD_SELF).
+        */
+       ASSERT_EQ(pthread_create(&thread, NULL, pidfd_self_thread_worker,
+                                (void *)page_size), 0);
+       ASSERT_EQ(pthread_join(thread, &res), 0);
+       err = (int)(intptr_t)res;
+
+       ASSERT_EQ(err, 0);
+}
+
  #if __NR_pidfd_getfd == -1
  int main(void)
  {
diff --git a/tools/testing/selftests/pidfd/pidfd_setns_test.c 
b/tools/testing/selftests/pidfd/pidfd_setns_test.c
index 7c2a4349170a..bbd39dc5ceb7 100644
--- a/tools/testing/selftests/pidfd/pidfd_setns_test.c
+++ b/tools/testing/selftests/pidfd/pidfd_setns_test.c
@@ -752,4 +752,15 @@ TEST(setns_einval)
        close(fd);
  }
+TEST(setns_pidfd_self_disallowed)
+{
+       ASSERT_EQ(setns(PIDFD_SELF_THREAD, 0), -1);
+       EXPECT_EQ(errno, EBADF);
+
+       errno = 0;
+
+       ASSERT_EQ(setns(PIDFD_SELF_THREAD_GROUP, 0), -1);
+       EXPECT_EQ(errno, EBADF);
+}
+
  TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/pidfd/pidfd_test.c 
b/tools/testing/selftests/pidfd/pidfd_test.c
index 9faa686f90e4..ab5caa0368a1 100644
--- a/tools/testing/selftests/pidfd/pidfd_test.c
+++ b/tools/testing/selftests/pidfd/pidfd_test.c
@@ -42,12 +42,41 @@ static pid_t pidfd_clone(int flags, int *pidfd, int 
(*fn)(void *))
  #endif
  }
-static int signal_received;
+static pthread_t signal_received;
static void set_signal_received_on_sigusr1(int sig)
  {
        if (sig == SIGUSR1)
-               signal_received = 1;
+               signal_received = pthread_self();
+}
+
+static int send_signal(int pidfd)
+{
+       int ret = 0;
+
+       if (sys_pidfd_send_signal(pidfd, SIGUSR1, NULL, 0) < 0) {
+               ret = -EINVAL;
+               goto exit;
+       }
+
+       if (signal_received != pthread_self()) {
+               ret = -EINVAL;
+               goto exit;
+       }
+
+exit:
+       signal_received = 0;
+       return ret;
+}
+
+static void *send_signal_worker(void *arg)
+{
+       int pidfd = (int)(intptr_t)arg;
+       int ret;
+
+       ret = send_signal(pidfd);
+

Same here - don't you have to check ret?

+       return (void *)(intptr_t)ret;
  }
/*
@@ -56,8 +85,11 @@ static void set_signal_received_on_sigusr1(int sig)
   */
  static int test_pidfd_send_signal_simple_success(void)
  {
-       int pidfd, ret;
+       int pidfd;
        const char *test_name = "pidfd_send_signal send SIGUSR1";
+       pthread_t thread;
+       void *thread_res;
+       int res;
if (!have_pidfd_send_signal) {
                ksft_test_result_skip(
@@ -74,17 +106,34 @@ static int test_pidfd_send_signal_simple_success(void)
signal(SIGUSR1, set_signal_received_on_sigusr1); - ret = sys_pidfd_send_signal(pidfd, SIGUSR1, NULL, 0);
+       send_signal(pidfd);
        close(pidfd);
-       if (ret < 0)
-               ksft_exit_fail_msg("%s test: Failed to send signal\n",
+
+       /* Now try the same thing only using PIDFD_SELF_THREAD_GROUP. */
+       res = send_signal(PIDFD_SELF_THREAD_GROUP);
+       if (res)
+               ksft_exit_fail_msg(
+                       "%s test: Error %d on PIDFD_SELF_THREAD_GROUP signal\n",
+                       test_name, res);
+
+       /*
+        * Now try the same thing in a thread and assert thread ID is equal to
+        * worker thread ID.
+        */
+       if (pthread_create(&thread, NULL, send_signal_worker,
+                          (void *)(intptr_t)PIDFD_SELF_THREAD))
+               ksft_exit_fail_msg("%s test: Failed to create thread\n",
                                   test_name);
- if (signal_received != 1)
-               ksft_exit_fail_msg("%s test: Failed to receive signal\n",
+       if (pthread_join(thread, &thread_res))
+               ksft_exit_fail_msg("%s test: Failed to join thread\n",
                                   test_name);
+       res = (int)(intptr_t)thread_res;
+       if (res)
+               ksft_exit_fail_msg(
+                       "%s test: Error %d on PIDFD_SELF_THREAD signal\n",
+                       test_name, res);
- signal_received = 0;
        ksft_test_result_pass("%s test: Sent signal\n", test_name);
        return 0;
  }

thanks,
-- Shuah

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