pam: determine user cgroup tree from cgroup of PID 1

4 files changed, 70 insertions, 12 deletions

diff --git a/src/cgroup-util.c b/src/cgroup-util.c
index 055c906106..bbadc789a1 100644
--- a/src/cgroup-util.c
+++ b/src/cgroup-util.c
@@ -967,3 +967,31 @@ int cg_fix_path(const char *path, char **result) {
 
         return r;
 }
+
+int cg_get_user_path(char **path) {
+        char *root, *p;
+
+        assert(path);
+
+        /* Figure out the place to put user cgroups below. We use the
+         * same as PID 1 has but with the "/system" suffix replaced by
+         * "/user" */
+
+        if (cg_get_by_pid(SYSTEMD_CGROUP_CONTROLLER, 1, &root) < 0)
+                p = strdup("/user");
+        else {
+                if (endswith(root, "/system"))
+                        root[strlen(root) - 7] = 0;
+                else if (streq(root, "/"))
+                        root[0] = 0;
+
+                p = strappend(root, "/user");
+                free(root);
+        }
+
+        if (!p)
+                return -ENOMEM;
+
+        *path = p;
+        return 0;
+}
diff --git a/src/cgroup-util.h b/src/cgroup-util.h
index 73df9697ed..1eccbc9fd7 100644
--- a/src/cgroup-util.h
+++ b/src/cgroup-util.h
@@ -68,4 +68,6 @@ int cg_install_release_agent(const char *controller, const char *agent);
 int cg_is_empty(const char *controller, const char *path, bool ignore_self);
 int cg_is_empty_recursive(const char *controller, const char *path, bool ignore_self);
 
+int cg_get_user_path(char **path);
+
 #endif
diff --git a/src/pam-module.c b/src/pam-module.c
index e1a1a5001c..3a5404db4d 100644
--- a/src/pam-module.c
+++ b/src/pam-module.c
@@ -199,10 +199,8 @@ static int open_file_and_lock(const char *fn) {
          * locally accessible, and most likely even tmpfs. */
 
         if (flock(fd, LOCK_EX) < 0) {
-                int r = -errno;
-
                 close_nointr_nofail(fd);
-                return r;
+                return -errno;
         }
 
         return fd;
@@ -275,6 +273,7 @@ static uint64_t get_session_id(int *mode) {
         /* Last attempt, pick a random value */
         return (uint64_t) random_ull();
 }
+
 static int get_user_data(
                 pam_handle_t *handle,
                 const char **ret_username,
@@ -398,6 +397,7 @@ _public_ PAM_EXTERN int pam_sm_open_session(
         int lock_fd = -1;
         bool create_session = true;
         char **controllers = NULL, **reset_controllers = NULL, **c;
+        char *cgroup_user_tree = NULL;
 
         assert(handle);
 
@@ -417,6 +417,12 @@ _public_ PAM_EXTERN int pam_sm_open_session(
         if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
                 goto finish;
 
+        if ((r = cg_get_user_path(&cgroup_user_tree)) < 0) {
+                pam_syslog(handle, LOG_ERR, "Failed to determine user cgroup tree: %s", strerror(-r));
+                r = PAM_SYSTEM_ERR;
+                goto finish;
+        }
+
         if (safe_mkdir(RUNTIME_DIR "/user", 0755, 0, 0) < 0) {
                 pam_syslog(handle, LOG_ERR, "Failed to create runtime directory: %m");
                 r = PAM_SYSTEM_ERR;
@@ -480,9 +486,9 @@ _public_ PAM_EXTERN int pam_sm_open_session(
                         }
                 }
 
-                r = asprintf(&buf, "/user/%s/%s", username, id);
+                r = asprintf(&buf, "%s/%s/%s", cgroup_user_tree, username, id);
         } else
-                r = asprintf(&buf, "/user/%s/master", username);
+                r = asprintf(&buf, "%s/%s/master", cgroup_user_tree, username);
 
         if (r < 0) {
                 r = PAM_BUF_ERR;
@@ -513,6 +519,8 @@ finish:
         strv_free(controllers);
         strv_free(reset_controllers);
 
+        free(cgroup_user_tree);
+
         return r;
 }
 
@@ -604,6 +612,7 @@ _public_ PAM_EXTERN int pam_sm_close_session(
         struct passwd *pw;
         const void *created = NULL;
         char **controllers = NULL, **c, **kill_only_users = NULL, **kill_exclude_users = NULL;
+        char *cgroup_user_tree = NULL;
 
         assert(handle);
 
@@ -621,6 +630,12 @@ _public_ PAM_EXTERN int pam_sm_close_session(
         if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
                 goto finish;
 
+        if ((r = cg_get_user_path(&cgroup_user_tree)) < 0) {
+                pam_syslog(handle, LOG_ERR, "Failed to determine user cgroup tree: %s", strerror(-r));
+                r = PAM_SYSTEM_ERR;
+                goto finish;
+        }
+
         if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) {
                 pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m");
                 r = PAM_SYSTEM_ERR;
@@ -628,14 +643,14 @@ _public_ PAM_EXTERN int pam_sm_close_session(
         }
 
         /* We are probably still in some session/user dir. Move ourselves out of the way as first step */
-        if ((r = cg_attach(SYSTEMD_CGROUP_CONTROLLER, "/user", 0)) < 0)
+        if ((r = cg_attach(SYSTEMD_CGROUP_CONTROLLER, cgroup_user_tree, 0)) < 0)
                 pam_syslog(handle, LOG_ERR, "Failed to move us away: %s", strerror(-r));
 
         STRV_FOREACH(c, controllers)
-                if ((r = cg_attach(*c, "/user", 0)) < 0)
+                if ((r = cg_attach(*c, cgroup_user_tree, 0)) < 0)
                         pam_syslog(handle, LOG_ERR, "Failed to move us away in %s hierarchy: %s", *c, strerror(-r));
 
-        if (asprintf(&user_path, "/user/%s", username) < 0) {
+        if (asprintf(&user_path, "%s/%s", cgroup_user_tree, username) < 0) {
                 r = PAM_BUF_ERR;
                 goto finish;
         }
@@ -644,8 +659,8 @@ _public_ PAM_EXTERN int pam_sm_close_session(
 
         if ((id = pam_getenv(handle, "XDG_SESSION_ID")) && created) {
 
-                if (asprintf(&session_path, "/user/%s/%s", username, id) < 0 ||
-                    asprintf(&nosession_path, "/user/%s/master", username) < 0) {
+                if (asprintf(&session_path, "%s/%s/%s", cgroup_user_tree, username, id) < 0 ||
+                    asprintf(&nosession_path, "%s/%s/master", cgroup_user_tree, username) < 0) {
                         r = PAM_BUF_ERR;
                         goto finish;
                 }
@@ -731,5 +746,7 @@ finish:
         strv_free(kill_exclude_users);
         strv_free(kill_only_users);
 
+        free(cgroup_user_tree);
+
         return r;
 }
diff --git a/src/user-sessions.c b/src/user-sessions.c
index 8026961560..d3faad0cd6 100644
--- a/src/user-sessions.c
+++ b/src/user-sessions.c
@@ -57,14 +57,25 @@ int main(int argc, char*argv[]) {
 
         } else if (streq(argv[1], "stop")) {
                 int r, q;
+                char *cgroup_user_tree = NULL;
 
                 if ((r = write_one_line_file("/var/run/nologin", "System is going down.")) < 0)
                         log_error("Failed to create /var/run/nologin: %s", strerror(-r));
 
-                if ((q = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, "/user", true)) < 0)
+                if ((q = cg_get_user_path(&cgroup_user_tree)) < 0) {
+                        log_error("Failed to determine use path: %s", strerror(-q));
+                        goto finish;
+                }
+
+                q = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, cgroup_user_tree, true);
+                free(cgroup_user_tree);
+
+                if (q < 0) {
                         log_error("Failed to kill sessions: %s", strerror(-q));
+                        goto finish;
+                }
 
-                if (r < 0 || q < 0)
+                if (r < 0)
                         goto finish;
 
         } else {