From 80753fa3c0622fd8117c64e1ed2d7841edee3b00 Mon Sep 17 00:00:00 2001

From: Lennart Poettering <lennart@poettering.net>

Date: Thu, 13 Nov 2014 14:34:42 +0100

Subject: [PATCH] core: introduce new Delegate=yes/no property controlling

 creation of cgroup subhierarchies

For priviliged units this resource control property ensures that the

processes have all controllers systemd manages enabled.

For unpriviliged services (those with User= set) this ensures that

access rights to the service cgroup is granted to the user in question,

to create further subgroups. Note that this only applies to the

name=systemd hierarchy though, as access to other controllers is not

safe for unpriviliged processes.

Delegate=yes should be set for container scopes where a systemd instance

inside the container shall manage the hierarchies below its own cgroup

and have access to all controllers.

Delegate=yes should also be set for user@.service, so that systemd

--user can run, controlling its own cgroup tree.

This commit changes machined, systemd-nspawn@.service and user@.service

to set this boolean, in order to ensure that container management will

just work, and the user systemd instance can run fine.

(cherry picked from a931ad47a8623163a29d898224d8a8c1177ffdaf)

Resolves: #1179715

---

 man/systemd.resource-control.xml      | 14 ++++++++++++

 src/core/cgroup.c                     | 19 +++++++++++++++--

 src/core/cgroup.h                     |  2 ++

 src/core/dbus-cgroup.c                | 40 +++++++++++++++++++++++++++++++++++

 src/core/execute.c                    | 23 +++++++++++++++++---

 src/core/execute.h                    |  2 ++

 src/core/load-fragment-gperf.gperf.m4 |  3 ++-

 src/core/mount.c                      |  1 +

 src/core/service.c                    |  1 +

 src/core/socket.c                     |  1 +

 src/core/swap.c                       |  1 +

 src/machine/machined-dbus.c           | 10 +++++++++

 src/shared/cgroup-util.h              |  3 ++-

 units/systemd-nspawn@.service.in      |  1 +

 14 files changed, 114 insertions(+), 7 deletions(-)

diff --git a/man/systemd.resource-control.xml b/man/systemd.resource-control.xml

index 8688905..3748c0c 100644

--- a/man/systemd.resource-control.xml

+++ b/man/systemd.resource-control.xml

@@ -327,6 +327,20 @@ along with systemd; If not, see <http://www.gnu.org/licenses/>.

         </listitem>

       </varlistentry>

+      <varlistentry>

+        <term><varname>Delegate=</varname></term>

+

+        <listitem>

+          <para>Turns on delegation of further resource control

+          partitioning to processes of the unit. For unpriviliged

+          services (i.e. those using the <varname>User=</varname>

+          setting) this allows processes to create a subhierarchy

+          beneath its control group path. For priviliged services and

+          scopes this ensures the processes will have all control

+          group controllers enabled.</para>

+        </listitem>

+      </varlistentry>

+

     </variablelist>

   </refsect1>

diff --git a/src/core/cgroup.c b/src/core/cgroup.c

index 32e2599..764311f 100644

--- a/src/core/cgroup.c

+++ b/src/core/cgroup.c

@@ -94,14 +94,16 @@ void cgroup_context_dump(CGroupContext *c, FILE* f, const char *prefix) {

                 "%sCPUShares=%lu\n"

                 "%sBlockIOWeight=%lu\n"

                 "%sMemoryLimit=%" PRIu64 "\n"

-                "%sDevicePolicy=%s\n",

+                "%sDevicePolicy=%s\n"

+                "%sDelegate=%s\n",

                 prefix, yes_no(c->cpu_accounting),

                 prefix, yes_no(c->blockio_accounting),

                 prefix, yes_no(c->memory_accounting),

                 prefix, c->cpu_shares,

                 prefix, c->blockio_weight,

                 prefix, c->memory_limit,

-                prefix, cgroup_device_policy_to_string(c->device_policy));

+                prefix, cgroup_device_policy_to_string(c->device_policy),

+                prefix, yes_no(c->delegate));

         LIST_FOREACH(device_allow, a, c->device_allow)

                 fprintf(f,

@@ -342,6 +344,19 @@ static CGroupControllerMask unit_get_cgroup_mask(Unit *u) {

         if (!c)

                 return 0;

+        /* If delegation is turned on, then turn on all cgroups,

+         * unless the process we fork into it is known to drop

+         * privileges anyway, and shouldn't get access to the

+         * controllers anyway. */

+

+        if (c->delegate) {

+                ExecContext *e;

+

+                e = unit_get_exec_context(u);

+                if (!e || exec_context_maintains_privileges(e))

+                        return _CGROUP_CONTROLLER_MASK_ALL;

+        }

+

         return cgroup_context_get_mask(c);

 }

diff --git a/src/core/cgroup.h b/src/core/cgroup.h

index 0a079e9..d00bcac 100644

--- a/src/core/cgroup.h

+++ b/src/core/cgroup.h

@@ -80,6 +80,8 @@ struct CGroupContext {

         CGroupDevicePolicy device_policy;

         LIST_HEAD(CGroupDeviceAllow, device_allow);

+

+        bool delegate;

 };

 #include "unit.h"

diff --git a/src/core/dbus-cgroup.c b/src/core/dbus-cgroup.c

index 9ebcad9..a13c869 100644

--- a/src/core/dbus-cgroup.c

+++ b/src/core/dbus-cgroup.c

@@ -124,6 +124,7 @@ static int bus_cgroup_append_device_allow(DBusMessageIter *i, const char *proper

 }

 const BusProperty bus_cgroup_context_properties[] = {

+        { "Delegate",                bus_property_append_bool,            "b",     offsetof(CGroupContext, delegate)           },

         { "CPUAccounting",           bus_property_append_bool,            "b",     offsetof(CGroupContext, cpu_accounting)     },

         { "CPUShares",               bus_property_append_ul,              "t",     offsetof(CGroupContext, cpu_shares)         },

         { "BlockIOAccounting",       bus_property_append_bool,            "b",     offsetof(CGroupContext, blockio_accounting) },

@@ -138,6 +139,38 @@ const BusProperty bus_cgroup_context_properties[] = {

         {}

 };

+static int bus_cgroup_set_transient_property(

+                Unit *u,

+                CGroupContext *c,

+                const char *name,

+                DBusMessageIter *i,

+                UnitSetPropertiesMode mode,

+                DBusError *error) {

+

+        assert(u);

+        assert(c);

+        assert(name);

+        assert(i);

+

+        if (streq(name, "Delegate")) {

+

+                if (dbus_message_iter_get_arg_type(i) != DBUS_TYPE_BOOLEAN)

+                        return -EINVAL;

+

+                if (mode != UNIT_CHECK) {

+                        dbus_bool_t b;

+

+                        dbus_message_iter_get_basic(i, &b);

+                        c->delegate = b;

+                        unit_write_drop_in_private(u, mode, name, b ? "Delegate=yes" : "Delegate=no");

+                }

+

+                return 1;

+        }

+

+        return 0;

+}

+

 int bus_cgroup_set_property(

                 Unit *u,

                 CGroupContext *c,

@@ -550,5 +583,12 @@ int bus_cgroup_set_property(

                 return 1;

         }

+        if (u->transient && u->load_state == UNIT_STUB) {

+                int r;

+                r = bus_cgroup_set_transient_property(u, c, name, i, mode, error);

+                if (r != 0)

+                        return r;

+        }

+

         return 0;

 }

diff --git a/src/core/execute.c b/src/core/execute.c

index 981b9e4..c3fd6a8 100644

--- a/src/core/execute.c

+++ b/src/core/execute.c

@@ -1035,6 +1035,7 @@ int exec_spawn(ExecCommand *command,

                bool confirm_spawn,

                CGroupControllerMask cgroup_supported,

                const char *cgroup_path,

+               bool cgroup_delegate,

                const char *unit_id,

                int idle_pipe[4],

                pid_t *ret) {

@@ -1299,8 +1300,10 @@ int exec_spawn(ExecCommand *command,

                         }

                 }

-#ifdef HAVE_PAM

-                if (cgroup_path && context->user && context->pam_name) {

+                /* If delegation is enabled we'll pass ownership of the cgroup

+                 * (but only in systemd's own controller hierarchy!) to the

+                 * user of the new process. */

+               if (cgroup_path && context->user && cgroup_delegate) {

                         err = cg_set_task_access(SYSTEMD_CGROUP_CONTROLLER, cgroup_path, 0644, uid, gid);

                         if (err < 0) {

                                 r = EXIT_CGROUP;

@@ -1314,7 +1317,6 @@ int exec_spawn(ExecCommand *command,

                                 goto fail_child;

                         }

                 }

-#endif

                 if (apply_permissions) {

                         err = enforce_groups(context, username, gid);

@@ -2069,6 +2071,21 @@ void exec_context_dump(ExecContext *c, FILE* f, const char *prefix) {

                         prefix, c->utmp_id);

 }

+bool exec_context_maintains_privileges(ExecContext *c) {

+        assert(c);

+

+        /* Returns true if the process forked off would run under

+         * an unchanged UID or as root. */

+

+        if (!c->user)

+                return true;

+

+        if (streq(c->user, "root") || streq(c->user, "0"))

+                return true;

+

+        return false;

+}

+

 void exec_status_start(ExecStatus *s, pid_t pid) {

         assert(s);

diff --git a/src/core/execute.h b/src/core/execute.h

index c1e9717..eca9d7d 100644

--- a/src/core/execute.h

+++ b/src/core/execute.h

@@ -173,6 +173,7 @@ int exec_spawn(ExecCommand *command,

                bool confirm_spawn,

                CGroupControllerMask cgroup_mask,

                const char *cgroup_path,

+               bool cgroup_delegate,

                const char *unit_id,

                int pipe_fd[2],

                pid_t *ret);

@@ -199,6 +200,7 @@ void exec_context_tty_reset(const ExecContext *context);

 int exec_context_load_environment(const ExecContext *c, char ***l);

 bool exec_context_may_touch_console(ExecContext *c);

+bool exec_context_maintains_privileges(ExecContext *c);

 void exec_context_serialize(const ExecContext *c, Unit *u, FILE *f);

 void exec_status_start(ExecStatus *s, pid_t pid);

diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4

index 0991cb9..3e88c8a 100644

--- a/src/core/load-fragment-gperf.gperf.m4

+++ b/src/core/load-fragment-gperf.gperf.m4

@@ -95,7 +95,8 @@ $1.BlockIOAccounting,            config_parse_bool,                  0,

 $1.BlockIOWeight,                config_parse_blockio_weight,        0,                             offsetof($1, cgroup_context)

 $1.BlockIODeviceWeight,          config_parse_blockio_device_weight, 0,                             offsetof($1, cgroup_context)

 $1.BlockIOReadBandwidth,         config_parse_blockio_bandwidth,     0,                             offsetof($1, cgroup_context)

-$1.BlockIOWriteBandwidth,        config_parse_blockio_bandwidth,     0,                             offsetof($1, cgroup_context)'

+$1.BlockIOWriteBandwidth,        config_parse_blockio_bandwidth,     0,                             offsetof($1, cgroup_context)

+$1.Delegate,                     config_parse_bool,                  0,                             offsetof($1, cgroup_context.delegate)'

 )m4_dnl

 Unit.Description,                config_parse_unit_string_printf,    0,                             offsetof(Unit, description)

 Unit.Documentation,              config_parse_documentation,         0,                             offsetof(Unit, documentation)

diff --git a/src/core/mount.c b/src/core/mount.c

index 3672338..f7c98c4 100644

--- a/src/core/mount.c

+++ b/src/core/mount.c

@@ -793,6 +793,7 @@ static int mount_spawn(Mount *m, ExecCommand *c, pid_t *_pid) {

                        UNIT(m)->manager->confirm_spawn,

                        UNIT(m)->manager->cgroup_supported,

                        UNIT(m)->cgroup_path,

+                       m->cgroup_context.delegate,

                        UNIT(m)->id,

                        NULL,

                        &pid;;

diff --git a/src/core/service.c b/src/core/service.c

index f6fdbbc..da30d77 100644

--- a/src/core/service.c

+++ b/src/core/service.c

@@ -1869,6 +1869,7 @@ static int service_spawn(

                        UNIT(s)->manager->confirm_spawn,

                        UNIT(s)->manager->cgroup_supported,

                        path,

+                       s->cgroup_context.delegate,

                        UNIT(s)->id,

                        s->type == SERVICE_IDLE ? UNIT(s)->manager->idle_pipe : NULL,

                        &pid;;

diff --git a/src/core/socket.c b/src/core/socket.c

index 32e0d35..f365125 100644

--- a/src/core/socket.c

+++ b/src/core/socket.c

@@ -1229,6 +1229,7 @@ static int socket_spawn(Socket *s, ExecCommand *c, pid_t *_pid) {

                        UNIT(s)->manager->confirm_spawn,

                        UNIT(s)->manager->cgroup_supported,

                        UNIT(s)->cgroup_path,

+                       s->cgroup_context.delegate,

                        UNIT(s)->id,

                        NULL,

                        &pid;;

diff --git a/src/core/swap.c b/src/core/swap.c

index 727bb95..597c8ca 100644

--- a/src/core/swap.c

+++ b/src/core/swap.c

@@ -591,6 +591,7 @@ static int swap_spawn(Swap *s, ExecCommand *c, pid_t *_pid) {

                        UNIT(s)->manager->confirm_spawn,

                        UNIT(s)->manager->cgroup_supported,

                        UNIT(s)->cgroup_path,

+                       s->cgroup_context.delegate,

                        UNIT(s)->id,

                        NULL,

                        &pid;;

diff --git a/src/machine/machined-dbus.c b/src/machine/machined-dbus.c

index 22caadf..0cebdc5 100644

--- a/src/machine/machined-dbus.c

+++ b/src/machine/machined-dbus.c

@@ -739,9 +739,11 @@ int manager_start_scope(

         DBusMessageIter iter, sub, sub2, sub3, sub4;

         const char *timeout_stop_property = "TimeoutStopUSec";

         const char *pids_property = "PIDs";

+        const char *delegate_property = "Delegate";

         uint64_t timeout = 500 * USEC_PER_MSEC;

         const char *fail = "fail";

         uint32_t u;

+        dbus_bool_t b = 1;

         int r;

         assert(manager);

@@ -814,6 +816,14 @@ int manager_start_scope(

             !dbus_message_iter_close_container(&sub, &sub2))

                 return log_oom();

+        if (!dbus_message_iter_open_container(&sub, DBUS_TYPE_STRUCT, NULL, &sub2) ||

+            !dbus_message_iter_append_basic(&sub2, DBUS_TYPE_STRING, &delegate_property) ||

+            !dbus_message_iter_open_container(&sub2, DBUS_TYPE_VARIANT, "b", &sub3) ||

+            !dbus_message_iter_append_basic(&sub3, DBUS_TYPE_BOOLEAN, &b) ||

+            !dbus_message_iter_close_container(&sub2, &sub3) ||

+            !dbus_message_iter_close_container(&sub, &sub2))

+                return log_oom();

+

         if (more_properties) {

                 r = copy_many_fields(&sub, more_properties);

                 if (r < 0)

diff --git a/src/shared/cgroup-util.h b/src/shared/cgroup-util.h

index 0963450..0608b9a 100644

--- a/src/shared/cgroup-util.h

+++ b/src/shared/cgroup-util.h

@@ -34,7 +34,8 @@ typedef enum CGroupControllerMask {

         CGROUP_CPUACCT = 2,

         CGROUP_BLKIO = 4,

         CGROUP_MEMORY = 8,

-        CGROUP_DEVICE = 16

+        CGROUP_DEVICE = 16,

+        _CGROUP_CONTROLLER_MASK_ALL = 31

 } CGroupControllerMask;

 /*

diff --git a/units/systemd-nspawn@.service.in b/units/systemd-nspawn@.service.in

index 8e00736..bdfa89f 100644

--- a/units/systemd-nspawn@.service.in

+++ b/units/systemd-nspawn@.service.in

@@ -12,6 +12,7 @@ Documentation=man:systemd-nspawn(1)

 [Service]

 ExecStart=@bindir@/systemd-nspawn -bjD /var/lib/container/%i

 Type=notify

+Delegate=yes

 [Install]

 WantedBy=multi-user.target