sys-utils: cleanup license lines, add SPDX

[thirdparty/util-linux.git] / sys-utils / nsenter.c

diff --git a/sys-utils/nsenter.c b/sys-utils/nsenter.c
index 6f9558052cc4721d8ec4c433a6dd26473c553f68..73ada265b2b7ee6dd812f6b981f6f7aa751c9d08 100644 (file)
--- a/sys-utils/nsenter.c
+++ b/sys-utils/nsenter.c
@@ -1,22 +1,14 @@
 /*
- * nsenter(1) - command-line interface for setns(2)
- *
- * Copyright (C) 2012-2013 Eric Biederman <ebiederm@xmission.com>
+ * SPDX-License-Identifier: GPL-2.0
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
  * Free Software Foundation; version 2.
  *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
+ * Copyright (C) 2012-2023 Eric Biederman <ebiederm@xmission.com>
  *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ * nsenter(1) - command-line interface for setns(2)
  */
-
 #include <dirent.h>
 #include <errno.h>
 #include <getopt.h>
@@ -30,6 +22,7 @@
 #include <sys/wait.h>
 #include <grp.h>
 #include <sys/stat.h>
+#include <sys/statfs.h>
 
 #include <sys/ioctl.h>
 #ifdef HAVE_LINUX_NSFS_H
@@ -54,6 +47,8 @@
 #include "all-io.h"
 #include "env.h"
 #include "caputils.h"
+#include "statfs_magic.h"
+#include "pathnames.h"
 
 static struct namespace_file {
        int nstype;
@@ -111,13 +106,14 @@ static void __attribute__((__noreturn__)) usage(void)
        fputs(_(" -W, --wdns <dir>       set the working directory in namespace\n"), out);
        fputs(_(" -e, --env              inherit environment variables from target process\n"), out);
        fputs(_(" -F, --no-fork          do not fork before exec'ing <program>\n"), out);
+       fputs(_(" -c, --join-cgroup      join the cgroup of the target process\n"), out);
 #ifdef HAVE_LIBSELINUX
        fputs(_(" -Z, --follow-context   set SELinux context according to --target PID\n"), out);
 #endif
 
        fputs(USAGE_SEPARATOR, out);
-       printf(USAGE_HELP_OPTIONS(24));
-       printf(USAGE_MAN_TAIL("nsenter(1)"));
+       fprintf(out, USAGE_HELP_OPTIONS(24));
+       fprintf(out, USAGE_MAN_TAIL("nsenter(1)"));
 
        exit(EXIT_SUCCESS);
 }
@@ -127,6 +123,7 @@ static int root_fd = -1;
 static int wd_fd = -1;
 static int env_fd = -1;
 static int uid_gid_fd = -1;
+static int cgroup_procs_fd = -1;
 
 static void set_parent_user_ns_fd(void)
 {
@@ -202,6 +199,55 @@ static int get_ns_ino(const char *path, ino_t *ino)
        return 0;
 }
 
+static void open_cgroup_procs(void)
+{
+       char *buf = NULL, *path = NULL, *p;
+       int cgroup_fd = 0;
+       char fdpath[PATH_MAX];
+
+       open_target_fd(&cgroup_fd, "cgroup", optarg);
+
+       if (read_all_alloc(cgroup_fd, &buf) < 1)
+               err(EXIT_FAILURE, _("failed to get cgroup path"));
+
+       p = strtok(buf, "\n");
+       if (p)
+               path = strrchr(p, ':');
+       if (!path)
+               err(EXIT_FAILURE, _("failed to get cgroup path"));
+       path++;
+
+       snprintf(fdpath, sizeof(fdpath), _PATH_SYS_CGROUP "/%s/cgroup.procs", path);
+
+       if ((cgroup_procs_fd = open(fdpath, O_WRONLY | O_APPEND)) < 0)
+               err(EXIT_FAILURE, _("failed to open cgroup.procs"));
+
+       free(buf);
+}
+
+static int is_cgroup2(void)
+{
+       struct statfs fs_stat;
+       int rc;
+
+       rc = statfs(_PATH_SYS_CGROUP, &fs_stat);
+       if (rc)
+               err(EXIT_FAILURE, _("statfs %s failed"), _PATH_SYS_CGROUP);
+       return F_TYPE_EQUAL(fs_stat.f_type, STATFS_CGROUP2_MAGIC);
+}
+
+static void join_into_cgroup(void)
+{
+       pid_t pid;
+       char buf[ sizeof(stringify_value(UINT32_MAX)) ];
+       int len;
+
+       pid = getpid();
+       len = snprintf(buf, sizeof(buf), "%zu", (size_t) pid);
+       if (write_all(cgroup_procs_fd, buf, len))
+               err(EXIT_FAILURE, _("write cgroup.procs failed"));
+}
+
 static int is_usable_namespace(pid_t target, const struct namespace_file *nsfile)
 {
        char path[PATH_MAX];
@@ -294,6 +340,7 @@ int main(int argc, char *argv[])
                { "wdns", optional_argument, NULL, 'W' },
                { "env", no_argument, NULL, 'e' },
                { "no-fork", no_argument, NULL, 'F' },
+               { "join-cgroup", no_argument, NULL, 'c'},
                { "preserve-credentials", no_argument, NULL, OPT_PRESERVE_CRED },
                { "keep-caps", no_argument, NULL, OPT_KEEPCAPS },
                { "user-parent", no_argument, NULL, OPT_USER_PARENT},
@@ -312,7 +359,7 @@ int main(int argc, char *argv[])
        int c, pass, namespaces = 0, setgroups_nerrs = 0, preserve_cred = 0;
        bool do_rd = false, do_wd = false, do_uid = false, force_uid = false,
             do_gid = false, force_gid = false, do_env = false, do_all = false,
-            do_user_parent = false;
+            do_join_cgroup = false, do_user_parent = false;
        int do_fork = -1; /* unknown yet */
        char *wdns = NULL;
        uid_t uid = 0;
@@ -329,7 +376,7 @@ int main(int argc, char *argv[])
        close_stdout_atexit();
 
        while ((c =
-               getopt_long(argc, argv, "+ahVt:m::u::i::n::p::C::U::T::S:G:r::w::W::eFZ",
+               getopt_long(argc, argv, "+ahVt:m::u::i::n::p::C::U::T::S:G:r::w::W::ecFZ",
                            longopts, NULL)) != -1) {
 
                err_exclusive_options(c, longopts, excl, excl_st);
@@ -407,6 +454,9 @@ int main(int argc, char *argv[])
                case 'F':
                        do_fork = 0;
                        break;
+               case 'c':
+                       do_join_cgroup = true;
+                       break;
                case 'r':
                        if (optarg)
                                open_target_fd(&root_fd, "root", optarg);
@@ -491,6 +541,11 @@ int main(int argc, char *argv[])
                open_target_fd(&env_fd, "environ", NULL);
        if (do_uid || do_gid)
                open_target_fd(&uid_gid_fd, "", NULL);
+       if (do_join_cgroup) {
+               if (!is_cgroup2())
+                       errx(EXIT_FAILURE, _("--join-cgroup is only supported in cgroup v2"));
+               open_cgroup_procs();
+       }
 
        /*
         * Get parent userns from any available ns.
@@ -598,6 +653,10 @@ int main(int argc, char *argv[])
                close(env_fd);
        }
 
+       // Join into the target cgroup
+       if (cgroup_procs_fd >= 0)
+               join_into_cgroup();
+
        if (uid_gid_fd >= 0) {
                struct stat st;