1 files changed, 33 insertions, 14 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7dc8788cfd52..940aced4ed00 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1035,6 +1035,11 @@ static void cgroup_get(struct cgroup *cgrp)
         css_get(&cgrp->self);
 }
 
+static bool cgroup_tryget(struct cgroup *cgrp)
+{
+        return css_tryget(&cgrp->self);
+}
+
 static void cgroup_put(struct cgroup *cgrp)
 {
         css_put(&cgrp->self);
@@ -1147,7 +1152,8 @@ static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn)
          * protection against removal.  Ensure @cgrp stays accessible and
          * break the active_ref protection.
          */
-        cgroup_get(cgrp);
+        if (!cgroup_tryget(cgrp))
+                return NULL;
         kernfs_break_active_protection(kn);
 
         mutex_lock(&cgroup_mutex);
@@ -3271,8 +3277,17 @@ int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 {
         struct cftype *cft;
 
-        for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
-                cft->flags |= __CFTYPE_NOT_ON_DFL;
+        /*
+         * If legacy_flies_on_dfl, we want to show the legacy files on the
+         * dfl hierarchy but iff the target subsystem hasn't been updated
+         * for the dfl hierarchy yet.
+         */
+        if (!cgroup_legacy_files_on_dfl ||
+            ss->dfl_cftypes != ss->legacy_cftypes) {
+                for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
+                        cft->flags |= __CFTYPE_NOT_ON_DFL;
+        }
+
         return cgroup_add_cftypes(ss, cfts);
 }
 
@@ -4387,6 +4402,15 @@ static void css_release_work_fn(struct work_struct *work)
                 /* cgroup release path */
                 cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
                 cgrp->id = -1;
+
+                /*
+                 * There are two control paths which try to determine
+                 * cgroup from dentry without going through kernfs -
+                 * cgroupstats_build() and css_tryget_online_from_dir().
+                 * Those are supported by RCU protecting clearing of
+                 * cgrp->kn->priv backpointer.
+                 */
+                RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL);
         }
 
         mutex_unlock(&cgroup_mutex);
@@ -4543,6 +4567,11 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
         struct cftype *base_files;
         int ssid, ret;
 
+        /* Do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable.
+         */
+        if (strchr(name, '\n'))
+                return -EINVAL;
+
         parent = cgroup_kn_lock_live(parent_kn);
         if (!parent)
                 return -ENODEV;
@@ -4820,16 +4849,6 @@ static int cgroup_rmdir(struct kernfs_node *kn)
 
         cgroup_kn_unlock(kn);
 
-        /*
-         * There are two control paths which try to determine cgroup from
-         * dentry without going through kernfs - cgroupstats_build() and
-         * css_tryget_online_from_dir().  Those are supported by RCU
-         * protecting clearing of cgrp->kn->priv backpointer, which should
-         * happen after all files under it have been removed.
-         */
-        if (!ret)
-                RCU_INIT_POINTER(*(void __rcu __force **)&kn->priv, NULL);
-
         cgroup_put(cgrp);
         return ret;
 }
@@ -5416,7 +5435,7 @@ struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
         /*
          * This path doesn't originate from kernfs and @kn could already
          * have been or be removed at any point.  @kn->priv is RCU
-         * protected for this access.  See cgroup_rmdir() for details.
+         * protected for this access.  See css_release_work_fn() for details.
          */
         cgrp = rcu_dereference(kn->priv);
         if (cgrp)