cgroup: update cgroup name handling

Straightforward updates to cgroup name handling in preparation of
kernfs conversion.

* cgroup_alloc_name() is updated to take const char * isntead of
  dentry * for name source.

* cgroup name formatting is separated out into cgroup_file_name().
  While at it, buffer length protection is added.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

1 files changed, 22 insertions, 13 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 0a178cd1f836..3f204429d108 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -67,6 +67,9 @@
  */
 #define CGROUP_PIDLIST_DESTROY_DELAY    HZ
 
+#define CGROUP_FILE_NAME_MAX            (MAX_CGROUP_TYPE_NAMELEN +      \
+                                         MAX_CFTYPE_NAME + 2)
+
 /*
  * cgroup_tree_mutex nests above cgroup_mutex and protects cftypes, file
  * creation/removal and hierarchy changing operations including cgroup
@@ -799,17 +802,29 @@ static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
         return inode;
 }
 
-static struct cgroup_name *cgroup_alloc_name(struct dentry *dentry)
+static struct cgroup_name *cgroup_alloc_name(const char *name_str)
 {
         struct cgroup_name *name;
 
-        name = kmalloc(sizeof(*name) + dentry->d_name.len + 1, GFP_KERNEL);
+        name = kmalloc(sizeof(*name) + strlen(name_str) + 1, GFP_KERNEL);
         if (!name)
                 return NULL;
-        strcpy(name->name, dentry->d_name.name);
+        strcpy(name->name, name_str);
         return name;
 }
 
+static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
+                              char *buf)
+{
+        if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
+            !(cgrp->root->flags & CGRP_ROOT_NOPREFIX))
+                snprintf(buf, CGROUP_FILE_NAME_MAX, "%s.%s",
+                         cft->ss->name, cft->name);
+        else
+                strncpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
+        return buf;
+}
+
 static void cgroup_free_fn(struct work_struct *work)
 {
         struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work);
@@ -2437,7 +2452,7 @@ static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
         if (cgroup_sane_behavior(cgrp))
                 return -EPERM;
 
-        name = cgroup_alloc_name(new_dentry);
+        name = cgroup_alloc_name(new_dentry->d_name.name);
         if (!name)
                 return -ENOMEM;
 
@@ -2613,14 +2628,7 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
         struct cfent *cfe;
         int error;
         umode_t mode;
-        char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
-
-        if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
-            !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
-                strcpy(name, cft->ss->name);
-                strcat(name, ".");
-        }
-        strcat(name, cft->name);
+        char name[CGROUP_FILE_NAME_MAX];
 
         BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
 
@@ -2628,6 +2636,7 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
         if (!cfe)
                 return -ENOMEM;
 
+        cgroup_file_name(cgrp, cft, name);
         dentry = lookup_one_len(name, dir, strlen(name));
         if (IS_ERR(dentry)) {
                 error = PTR_ERR(dentry);
@@ -4135,7 +4144,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
         if (!cgrp)
                 return -ENOMEM;
 
-        name = cgroup_alloc_name(dentry);
+        name = cgroup_alloc_name(dentry->d_name.name);
         if (!name) {
                 err = -ENOMEM;
                 goto err_free_cgrp;