This adds basic tests for the new close_range() syscall.
- test that no invalid flags can be passed
- test that a range of file descriptors is correctly closed
- test that a range of file descriptors is correctly closed if there there
  are already closed file descriptors in the range
- test that max_fd is correctly capped to the current fdtable maximum

Signed-off-by: Christian Brauner <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: David Howells <[email protected]>
Cc: Dmitry V. Levin <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Florian Weimer <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
/* v2 */
unchanged

/* v3 */
- Christian Brauner <[email protected]>:
  - verify that close_range() correctly closes a single file descriptor

/* v4 */
- Christian Brauner <[email protected]>:
  - add missing Cc for Shuah
  - add missing Cc for linux-kselftest

/* v5 */
- Michael Ellerman <[email protected]>:
  - remove include of unexported kernel headers
- Christian Brauner <[email protected]>:
  - add missing SPDX header to Makefile
---
 tools/testing/selftests/Makefile              |   1 +
 tools/testing/selftests/core/.gitignore       |   1 +
 tools/testing/selftests/core/Makefile         |   7 +
 .../testing/selftests/core/close_range_test.c | 149 ++++++++++++++++++
 4 files changed, 158 insertions(+)
 create mode 100644 tools/testing/selftests/core/.gitignore
 create mode 100644 tools/testing/selftests/core/Makefile
 create mode 100644 tools/testing/selftests/core/close_range_test.c

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 2ff68702fd41..2e387ce83311 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -6,6 +6,7 @@ TARGETS += breakpoints
 TARGETS += capabilities
 TARGETS += cgroup
 TARGETS += clone3
+TARGETS += core
 TARGETS += cpufreq
 TARGETS += cpu-hotplug
 TARGETS += drivers/dma-buf
diff --git a/tools/testing/selftests/core/.gitignore 
b/tools/testing/selftests/core/.gitignore
new file mode 100644
index 000000000000..6e6712ce5817
--- /dev/null
+++ b/tools/testing/selftests/core/.gitignore
@@ -0,0 +1 @@
+close_range_test
diff --git a/tools/testing/selftests/core/Makefile 
b/tools/testing/selftests/core/Makefile
new file mode 100644
index 000000000000..f6f2d6f473c6
--- /dev/null
+++ b/tools/testing/selftests/core/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0-only
+CFLAGS += -g -I../../../../usr/include/
+
+TEST_GEN_PROGS := close_range_test
+
+include ../lib.mk
+
diff --git a/tools/testing/selftests/core/close_range_test.c 
b/tools/testing/selftests/core/close_range_test.c
new file mode 100644
index 000000000000..6d92e239a228
--- /dev/null
+++ b/tools/testing/selftests/core/close_range_test.c
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/kernel.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syscall.h>
+#include <unistd.h>
+
+#include "../kselftest.h"
+
+#ifndef __NR_close_range
+#define __NR_close_range -1
+#endif
+
+static inline int sys_close_range(unsigned int fd, unsigned int max_fd,
+                                 unsigned int flags)
+{
+       return syscall(__NR_close_range, fd, max_fd, flags);
+}
+
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+#endif
+
+int main(int argc, char **argv)
+{
+       const char *test_name = "close_range";
+       int i, ret;
+       int open_fds[101];
+       int fd_max, fd_mid, fd_min;
+
+       ksft_set_plan(9);
+
+       for (i = 0; i < ARRAY_SIZE(open_fds); i++) {
+               int fd;
+
+               fd = open("/dev/null", O_RDONLY | O_CLOEXEC);
+               if (fd < 0) {
+                       if (errno == ENOENT)
+                               ksft_exit_skip(
+                                       "%s test: skipping test since /dev/null 
does not exist\n",
+                                       test_name);
+
+                       ksft_exit_fail_msg(
+                               "%s test: %s - failed to open /dev/null\n",
+                               strerror(errno), test_name);
+               }
+
+               open_fds[i] = fd;
+       }
+
+       fd_min = open_fds[0];
+       fd_max = open_fds[99];
+
+       ret = sys_close_range(fd_min, fd_max, 1);
+       if (!ret)
+               ksft_exit_fail_msg(
+                       "%s test: managed to pass invalid flag value\n",
+                       test_name);
+       if (errno == ENOSYS)
+               ksft_exit_skip("%s test: close_range() syscall not 
supported\n", test_name);
+
+       ksft_test_result_pass("do not allow invalid flag values for 
close_range()\n");
+
+       fd_mid = open_fds[50];
+       ret = sys_close_range(fd_min, fd_mid, 0);
+       if (ret < 0)
+               ksft_exit_fail_msg(
+                       "%s test: Failed to close range of file descriptors 
from %d to %d\n",
+                       test_name, fd_min, fd_mid);
+       ksft_test_result_pass("close_range() from %d to %d\n", fd_min, fd_mid);
+
+       for (i = 0; i <= 50; i++) {
+               ret = fcntl(open_fds[i], F_GETFL);
+               if (ret >= 0)
+                       ksft_exit_fail_msg(
+                               "%s test: Failed to close range of file 
descriptors from %d to %d\n",
+                               test_name, fd_min, fd_mid);
+       }
+       ksft_test_result_pass("fcntl() verify closed range from %d to %d\n", 
fd_min, fd_mid);
+
+       /* create a couple of gaps */
+       close(57);
+       close(78);
+       close(81);
+       close(82);
+       close(84);
+       close(90);
+
+       fd_mid = open_fds[51];
+       /* Choose slightly lower limit and leave some fds for a later test */
+       fd_max = open_fds[92];
+       ret = sys_close_range(fd_mid, fd_max, 0);
+       if (ret < 0)
+               ksft_exit_fail_msg(
+                       "%s test: Failed to close range of file descriptors 
from 51 to 100\n",
+                       test_name);
+       ksft_test_result_pass("close_range() from %d to %d\n", fd_mid, fd_max);
+
+       for (i = 51; i <= 92; i++) {
+               ret = fcntl(open_fds[i], F_GETFL);
+               if (ret >= 0)
+                       ksft_exit_fail_msg(
+                               "%s test: Failed to close range of file 
descriptors from 51 to 100\n",
+                               test_name);
+       }
+       ksft_test_result_pass("fcntl() verify closed range from %d to %d\n", 
fd_mid, fd_max);
+
+       fd_mid = open_fds[93];
+       fd_max = open_fds[99];
+       /* test that the kernel caps and still closes all fds */
+       ret = sys_close_range(fd_mid, UINT_MAX, 0);
+       if (ret < 0)
+               ksft_exit_fail_msg(
+                       "%s test: Failed to close range of file descriptors 
from 51 to 100\n",
+                       test_name);
+       ksft_test_result_pass("close_range() from %d to %d\n", fd_mid, fd_max);
+
+       for (i = 93; i < 100; i++) {
+               ret = fcntl(open_fds[i], F_GETFL);
+               if (ret >= 0)
+                       ksft_exit_fail_msg(
+                               "%s test: Failed to close range of file 
descriptors from 51 to 100\n",
+                               test_name);
+       }
+       ksft_test_result_pass("fcntl() verify closed range from %d to %d\n", 
fd_mid, fd_max);
+
+       ret = sys_close_range(open_fds[100], open_fds[100], 0);
+       if (ret < 0)
+               ksft_exit_fail_msg(
+                       "%s test: Failed to close single file descriptor\n",
+                       test_name);
+       ksft_test_result_pass("close_range() closed single file descriptor\n");
+
+       ret = fcntl(open_fds[100], F_GETFL);
+       if (ret >= 0)
+               ksft_exit_fail_msg(
+                       "%s test: Failed to close single file descriptor\n",
+                       test_name);
+       ksft_test_result_pass("fcntl() verify closed single file descriptor\n");
+
+       return ksft_exit_pass();
+}
-- 
2.26.2

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