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selftests/namespaces: first active reference count tests

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Test that initial namespaces can be reopened via file handle. Initial
namespaces should always have a ref count of one from boot.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-23-2e6f823ebdc0@kernel.org
Tested-by: syzbot@syzkaller.appspotmail.com
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2025-10-29 13:20:36 +01:00
parent e2b6e5eadc
commit 6bdce845fd
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GPG Key ID: 91C61BC06578DCA2
3 changed files with 79 additions and 1 deletions
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1
tools/testing/selftests/namespaces/.gitignore vendored
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@ -1,3 +1,4 @@
nsid_test
file_handle_test
init_ino_test
ns_active_ref_test

5
tools/testing/selftests/namespaces/Makefile
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@ -1,7 +1,10 @@
# SPDX-License-Identifier: GPL-2.0-only
CFLAGS += -Wall -O0 -g $(KHDR_INCLUDES) $(TOOLS_INCLUDES)
LDLIBS += -lcap
TEST_GEN_PROGS := nsid_test file_handle_test init_ino_test
TEST_GEN_PROGS := nsid_test file_handle_test init_ino_test ns_active_ref_test
include ../lib.mk
$(OUTPUT)/ns_active_ref_test: ../filesystems/utils.c

74
tools/testing/selftests/namespaces/ns_active_ref_test.c Normal file
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// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <linux/nsfs.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include "../kselftest_harness.h"
#include "../filesystems/utils.h"
#ifndef FD_NSFS_ROOT
#define FD_NSFS_ROOT -10003 /* Root of the nsfs filesystem */
#endif
/*
* Test that initial namespaces can be reopened via file handle.
* Initial namespaces should have active ref count of 1 from boot.
*/
TEST(init_ns_always_active)
{
struct file_handle *handle;
int mount_id;
int ret;
int fd1, fd2;
struct stat st1, st2;
handle = malloc(sizeof(*handle) + MAX_HANDLE_SZ);
ASSERT_NE(handle, NULL);
/* Open initial network namespace */
fd1 = open("/proc/1/ns/net", O_RDONLY);
ASSERT_GE(fd1, 0);
/* Get file handle for initial namespace */
handle->handle_bytes = MAX_HANDLE_SZ;
ret = name_to_handle_at(fd1, "", handle, &mount_id, AT_EMPTY_PATH);
if (ret < 0 && errno == EOPNOTSUPP) {
SKIP(free(handle); close(fd1);
return, "nsfs doesn't support file handles");
}
ASSERT_EQ(ret, 0);
/* Close the namespace fd */
close(fd1);
/* Try to reopen via file handle - should succeed since init ns is always active */
fd2 = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
if (fd2 < 0 && (errno == EINVAL || errno == EOPNOTSUPP)) {
SKIP(free(handle);
return, "open_by_handle_at with FD_NSFS_ROOT not supported");
}
ASSERT_GE(fd2, 0);
/* Verify we opened the same namespace */
fd1 = open("/proc/1/ns/net", O_RDONLY);
ASSERT_GE(fd1, 0);
ASSERT_EQ(fstat(fd1, &st1), 0);
ASSERT_EQ(fstat(fd2, &st2), 0);
ASSERT_EQ(st1.st_ino, st2.st_ino);
close(fd1);
close(fd2);
free(handle);
}
TEST_HARNESS_MAIN