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sd-login: add new sd_pid_get_cgroup() API 

This adds a new sd_pid_get_cgroup() call to sd-login which may be used
to query the control path of a process. This is useful for programs when
making use of delegation units, in order to figure out which subtree has
been delegated.

In light of the unified control group hierarchy this is finally safe to
do, hence let's add a proper API for it, to make it easier to use this.
This commit is contained in:
Lennart Poettering 2015-09-04 09:54:14 +02:00
parent 19af675e99
commit f5aaf57562
6 changed files with 102 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
Makefile-man.am
View File

@ -1937,6 +1937,7 @@ MANPAGES_ALIAS += \
man/sd_login_monitor_get_fd.3 \
man/sd_login_monitor_get_timeout.3 \
man/sd_login_monitor_unref.3 \
man/sd_peer_get_cgroup.3 \
man/sd_peer_get_machine_name.3 \
man/sd_peer_get_owner_uid.3 \
man/sd_peer_get_session.3 \
@ -1944,6 +1945,7 @@ MANPAGES_ALIAS += \
man/sd_peer_get_unit.3 \
man/sd_peer_get_user_slice.3 \
man/sd_peer_get_user_unit.3 \
man/sd_pid_get_cgroup.3 \
man/sd_pid_get_machine_name.3 \
man/sd_pid_get_owner_uid.3 \
man/sd_pid_get_slice.3 \
@ -1981,6 +1983,7 @@ man/sd_login_monitor_get_events.3: man/sd_login_monitor_new.3
man/sd_login_monitor_get_fd.3: man/sd_login_monitor_new.3
man/sd_login_monitor_get_timeout.3: man/sd_login_monitor_new.3
man/sd_login_monitor_unref.3: man/sd_login_monitor_new.3
man/sd_peer_get_cgroup.3: man/sd_pid_get_session.3
man/sd_peer_get_machine_name.3: man/sd_pid_get_session.3
man/sd_peer_get_owner_uid.3: man/sd_pid_get_session.3
man/sd_peer_get_session.3: man/sd_pid_get_session.3
@ -1988,6 +1991,7 @@ man/sd_peer_get_slice.3: man/sd_pid_get_session.3
man/sd_peer_get_unit.3: man/sd_pid_get_session.3
man/sd_peer_get_user_slice.3: man/sd_pid_get_session.3
man/sd_peer_get_user_unit.3: man/sd_pid_get_session.3
man/sd_pid_get_cgroup.3: man/sd_pid_get_session.3
man/sd_pid_get_machine_name.3: man/sd_pid_get_session.3
man/sd_pid_get_owner_uid.3: man/sd_pid_get_session.3
man/sd_pid_get_slice.3: man/sd_pid_get_session.3
@ -2043,6 +2047,9 @@ man/sd_login_monitor_get_timeout.html: man/sd_login_monitor_new.html
man/sd_login_monitor_unref.html: man/sd_login_monitor_new.html
$(html-alias)
man/sd_peer_get_cgroup.html: man/sd_pid_get_session.html
$(html-alias)
man/sd_peer_get_machine_name.html: man/sd_pid_get_session.html
$(html-alias)
@ -2064,6 +2071,9 @@ man/sd_peer_get_user_slice.html: man/sd_pid_get_session.html
man/sd_peer_get_user_unit.html: man/sd_pid_get_session.html
$(html-alias)
man/sd_pid_get_cgroup.html: man/sd_pid_get_session.html
$(html-alias)
man/sd_pid_get_machine_name.html: man/sd_pid_get_session.html
$(html-alias)

40
man/sd_pid_get_session.xml
View File

@ -50,6 +50,7 @@
<refname>sd_pid_get_machine_name</refname>
<refname>sd_pid_get_slice</refname>
<refname>sd_pid_get_user_slice</refname>
<refname>sd_pid_get_cgroup</refname>
<refname>sd_peer_get_session</refname>
<refname>sd_peer_get_unit</refname>
<refname>sd_peer_get_user_unit</refname>
@ -57,6 +58,7 @@
<refname>sd_peer_get_machine_name</refname>
<refname>sd_peer_get_slice</refname>
<refname>sd_peer_get_user_slice</refname>
<refname>sd_peer_get_cgroup</refname>
<refpurpose>Determine session, unit, owner of a session,
container/VM or slice of a specific PID or socket
peer</refpurpose>
@ -108,6 +110,12 @@
<paramdef>char **<parameter>slice</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_pid_get_cgroup</function></funcdef>
<paramdef>pid_t <parameter>pid</parameter></paramdef>
<paramdef>char **<parameter>cgroup</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_peer_get_session</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
@ -149,6 +157,12 @@
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>char **<parameter>slice</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_peer_get_cgroup</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>char **<parameter>cgroup</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
@ -217,6 +231,17 @@
returns the user slice (as managed by the user's systemd instance)
of a process.</para>
<para><function>sd_pid_get_cgroup()</function> returns the control
group path of the specified process, relative to the root of the
hierarchy. Returns the path without trailing slash, except for
processes located in the root control group, where "/" is
returned. To find the actual control group path in the file system
the returned path needs to be prefixed with
<filename>/sys/fs/cgroup/</filename> (if the unified control group
setup is used), or
<filename>/sys/fs/cgroup/<replaceable>HIERARCHY</replaceable>/</filename>
(if the legacy multi-hierarchy control group setup is used).</para>
<para>If the <varname>pid</varname> parameter of any of these
functions is passed as 0, the operation is executed for the
calling process.</para>
@ -226,13 +251,14 @@
<function>sd_peer_get_user_unit()</function>,
<function>sd_peer_get_owner_uid()</function>,
<function>sd_peer_get_machine_name()</function>,
<function>sd_peer_get_slice()</function> and
<function>sd_peer_get_user_slice()</function> calls operate
similar to their PID counterparts, but operate on a connected
AF_UNIX socket and retrieve information about the connected peer
process. Note that these fields are retrieved via
<filename>/proc</filename>, and hence are not suitable for
authorization purposes, as they are subject to races.</para>
<function>sd_peer_get_slice()</function>,
<function>sd_peer_get_user_slice()</function> and
<function>sd_peer_get_cgroup()</function> calls operate similar to
their PID counterparts, but operate on a connected AF_UNIX socket
and retrieve information about the connected peer process. Note
that these fields are retrieved via <filename>/proc</filename>,
and hence are not suitable for authorization purposes, as they are
subject to races.</para>
</refsect1>
<refsect1>

6
src/libsystemd/libsystemd.sym
View File

@ -467,3 +467,9 @@ global:
sd_bus_emit_object_removed;
sd_bus_flush_close_unref;
} LIBSYSTEMD_221;
LIBSYSTEMD_226 {
global:
sd_pid_get_cgroup;
sd_peer_get_cgroup;
} LIBSYSTEMD_222;

40
src/libsystemd/sd-login/sd-login.c
View File

@ -101,6 +101,32 @@ _public_ int sd_pid_get_owner_uid(pid_t pid, uid_t *uid) {
return cg_pid_get_owner_uid(pid, uid);
}
_public_ int sd_pid_get_cgroup(pid_t pid, char **cgroup) {
char *c;
int r;
assert_return(pid >= 0, -EINVAL);
assert_return(cgroup, -EINVAL);
r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid, &c);
if (r < 0)
return r;
/* The internal APIs return the empty string for the root
* cgroup, let's return the "/" in the public APIs instead, as
* that's easier and less ambigious for people to grok. */
if (isempty(c)) {
free(c);
c = strdup("/");
if (!c)
return -ENOMEM;
}
*cgroup = c;
return 0;
}
_public_ int sd_peer_get_session(int fd, char **session) {
struct ucred ucred = {};
int r;
@ -199,6 +225,20 @@ _public_ int sd_peer_get_user_slice(int fd, char **slice) {
return cg_pid_get_user_slice(ucred.pid, slice);
}
_public_ int sd_peer_get_cgroup(int fd, char **cgroup) {
struct ucred ucred;
int r;
assert_return(fd >= 0, -EBADF);
assert_return(cgroup, -EINVAL);
r = getpeercred(fd, &ucred);
if (r < 0)
return r;
return sd_pid_get_cgroup(ucred.pid, cgroup);
}
static int file_of_uid(uid_t uid, char **p) {
assert_return(uid_is_valid(uid), -EINVAL);

6
src/libsystemd/sd-login/test-login.c
View File

@ -33,7 +33,7 @@ static void test_login(void) {
_cleanup_free_ char *pp = NULL, *qq = NULL;
int r, k;
uid_t u, u2;
char *seat, *type, *class, *display, *remote_user, *remote_host, *display_session;
char *seat, *type, *class, *display, *remote_user, *remote_host, *display_session, *cgroup;
char *session;
char *state;
char *session2;
@ -50,6 +50,10 @@ static void test_login(void) {
assert_se(sd_pid_get_owner_uid(0, &u2) == 0);
printf("user = "UID_FMT"\n", u2);
assert_se(sd_pid_get_cgroup(0, &cgroup) == 0);
printf("cgroup = %s\n", cgroup);
free(cgroup);
display_session = NULL;
r = sd_uid_get_display(u2, &display_session);
assert_se(r >= 0 || r == -ENODATA);

8
src/systemd/sd-login.h
View File

@ -81,6 +81,10 @@ int sd_pid_get_user_slice(pid_t pid, char **slice);
* container. This will return an error for non-machine processes. */
int sd_pid_get_machine_name(pid_t pid, char **machine);
/* Get the control group from a PID, relative to the root of the
* hierarchy. */
int sd_pid_get_cgroup(pid_t pid, char **cgroup);
/* Similar to sd_pid_get_session(), but retrieves data about peer of
* connected AF_UNIX socket */
int sd_peer_get_session(int fd, char **session);
@ -109,6 +113,10 @@ int sd_peer_get_user_slice(int fd, char **slice);
* of connected AF_UNIX socket */
int sd_peer_get_machine_name(int fd, char **machine);
/* Similar to sd_pid_get_cgroup(), but retrieves data about the peer
* of a connected AF_UNIX socket. */
int sd_peer_get_cgroup(pid_t pid, char **cgroup);
/* Get state from UID. Possible states: offline, lingering, online, active, closing */
int sd_uid_get_state(uid_t uid, char **state);