libcgroup: ignore 'tasks' file when changing permission of control files

When cgroup_create_cgroup() is called with different control_fperm and
task_fperm, libcgroup first changes permissions of *all* files to match
the control_fperm, which includes the also the tasks file and it might
loose some permission bits. The tasks file is then modulated by
control_fperm, but because umask-style of control_fperm, it might get
lower permissions that users would expect.

Therefore 'tasks' file must be skipped when using control_fperm.

Changelog since v1:
  - use list of ignored files, cg_chmod_recursive_controller is called from
    cg_chmod_recursive, which should chmod all files, incl. 'tasks'.

Changelog since v2:
  - renamed the list with ignored files.

Signed-off-by: Jan Safranek <jsafrane@redhat.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>

diff --git a/src/api.c b/src/api.c
index 28486b71838a93492ae127f131b5a46d4211f85a..663c6a7c51ab2770d21210e77b3a287062459835 100644 (file)
--- a/src/api.c
+++ b/src/api.c
@@ -120,6 +120,8 @@ const char const *cgroup_strerror_codes[] = {
        "Value setting does not succeed",
 };
 
+static const char const *cgroup_ignored_tasks_files[] = { "tasks", NULL };
+
 static int cg_chown_file(FTS *fts, FTSENT *ent, uid_t owner, gid_t group)
 {
        int ret = 0;
@@ -240,17 +242,20 @@ int cg_chmod_file(FTS *fts, FTSENT *ent, mode_t dir_mode,
 }
 
 
-/*
- * TODO: Need to decide a better place to put this function.
+/**
+ * Changes permissions of all directories and control files (i.e. all
+ * files except files named in ignore_list. The list must be terminated with
+ * NULL.
  */
 static int cg_chmod_recursive_controller(char *path, mode_t dir_mode,
                int dirm_change, mode_t file_mode, int filem_change,
-               int owner_is_umask)
+               int owner_is_umask, const char const **ignore_list)
 {
        int ret = 0;
        int final_ret =0;
        FTS *fts;
        char *fts_path[2];
+       int i, ignored;
 
        fts_path[0] = path;
        fts_path[1] = NULL;
@@ -273,8 +278,19 @@ static int cg_chmod_recursive_controller(char *path, mode_t dir_mode,
                        }
                        break;
                }
+               ignored = 0;
+               if (ignore_list != NULL)
+                       for (i = 0; ignore_list[i] != NULL; i++)
+                               if (!strcmp(ignore_list[i], ent->fts_name)) {
+                                       ignored = 1;
+                                       break;
+                               }
+               if (ignored)
+                       continue;
+
                ret = cg_chmod_file(fts, ent, dir_mode, dirm_change,
-                       file_mode, filem_change, owner_is_umask);
+                               file_mode, filem_change,
+                               owner_is_umask);
                if (ret) {
                        last_errno = errno;
                        final_ret = ECGOTHER;
@@ -304,7 +320,7 @@ int cg_chmod_recursive(struct cgroup *cgroup, mode_t dir_mode,
                        break;
                }
                ret = cg_chmod_recursive_controller(path, dir_mode, dirm_change,
-                               file_mode, filem_change, 0);
+                               file_mode, filem_change, 0, NULL);
                if (ret)
                        final_ret = ret;
        }
@@ -1540,7 +1556,7 @@ int cgroup_create_cgroup(struct cgroup *cgroup, int ignore_ownership)
                                                cgroup->control_dperm != NO_PERMS,
                                                cgroup->control_fperm,
                                                cgroup->control_fperm != NO_PERMS,
-                                               1);
+                                               1, cgroup_ignored_tasks_files);
                }
 
                if (error)