Merge tag 'for-linus-2020-06-24' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull thread fix from Christian Brauner:
 "This fixes a regression introduced with 303cc571 ("nsproxy: attach
  to namespaces via pidfds").

  The LTP testsuite reported a regression where users would now see
  EBADF returned instead of EINVAL when an fd was passed that referred
  to an open file but the file was not a namespace file.

  Fix this by continuing to report EINVAL and add a regression test"

* tag 'for-linus-2020-06-24' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  tests: test for setns() EINVAL regression
  nsproxy: restore EINVAL for non-namespace file descriptor

kernel/nsproxy.c

@@ -531,7 +531,7 @@ SYSCALL_DEFINE2(setns, int, fd, int, flags)
 	} else if (!IS_ERR(pidfd_pid(file))) {
 		err = check_setns_flags(flags);
 	} else {
-		err = -EBADF;
+		err = -EINVAL;
 	}
 	if (err)
 		goto out;

tools/testing/selftests/pidfd/pidfd.h

@@ -95,4 +95,9 @@ static inline int sys_pidfd_getfd(int pidfd, int fd, int flags)
 	return syscall(__NR_pidfd_getfd, pidfd, fd, flags);
 }
 
+static inline int sys_memfd_create(const char *name, unsigned int flags)
+{
+	return syscall(__NR_memfd_create, name, flags);
+}
+
 #endif /* __PIDFD_H */

tools/testing/selftests/pidfd/pidfd_getfd_test.c

@@ -34,11 +34,6 @@ static int sys_kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1,
 	return syscall(__NR_kcmp, pid1, pid2, type, idx1, idx2);
 }
 
-static int sys_memfd_create(const char *name, unsigned int flags)
-{
-	return syscall(__NR_memfd_create, name, flags);
-}
-
 static int __child(int sk, int memfd)
 {
 	int ret;

tools/testing/selftests/pidfd/pidfd_setns_test.c

@@ -470,4 +470,16 @@ TEST_F(current_nsset, no_foul_play)
 	}
 }
 
+TEST(setns_einval)
+{
+	int fd;
+
+	fd = sys_memfd_create("rostock", 0);
+	EXPECT_GT(fd, 0);
+
+	ASSERT_NE(setns(fd, 0), 0);
+	EXPECT_EQ(errno, EINVAL);
+	close(fd);
+}
+
 TEST_HARNESS_MAIN