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kernfs: implement kernfs_get_parent(), kernfs_name/path() and friends

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kernfs_node->parent and ->name are currently marked as "published"
indicating that kernfs users may access them directly; however, those
fields may get updated by kernfs_rename[_ns]() and unrestricted access
may lead to erroneous values or oops.

Protect ->parent and ->name updates with a irq-safe spinlock
kernfs_rename_lock and implement the following accessors for these
fields.

* kernfs_name()		- format the node's name into the specified buffer
* kernfs_path()		- format the node's path into the specified buffer
* pr_cont_kernfs_name()	- pr_cont a node's name (doesn't need buffer)
* pr_cont_kernfs_path()	- pr_cont a node's path (doesn't need buffer)
* kernfs_get_parent()	- pin and return a node's parent

All can be called under any context.  The recursive sysfs_pathname()
in fs/sysfs/dir.c is replaced with kernfs_path() and
sysfs_rename_dir_ns() is updated to use kernfs_get_parent() instead of
dereferencing parent directly.

v2: Dummy definition of kernfs_path() for !CONFIG_KERNFS was missing
    static inline making it cause a lot of build warnings.  Add it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tejun Heo
2014-02-07 13:32:07 -05:00
committed by Greg Kroah-Hartman
parent 0c23b2259a
commit 3eef34ad7d
3 changed files with 203 additions and 42 deletions
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44
fs/sysfs/dir.c
View File

@@ -19,39 +19,18 @@
DEFINE_SPINLOCK(sysfs_symlink_target_lock);
/**
* sysfs_pathname - return full path to sysfs dirent
* @kn: kernfs_node whose path we want
* @path: caller allocated buffer of size PATH_MAX
*
* Gives the name "/" to the sysfs_root entry; any path returned
* is relative to wherever sysfs is mounted.
*/
static char *sysfs_pathname(struct kernfs_node *kn, char *path)
{
if (kn->parent) {
sysfs_pathname(kn->parent, path);
strlcat(path, "/", PATH_MAX);
}
strlcat(path, kn->name, PATH_MAX);
return path;
}
void sysfs_warn_dup(struct kernfs_node *parent, const char *name)
{
char *path;
char *buf, *path = NULL;
path = kzalloc(PATH_MAX, GFP_KERNEL);
if (path) {
sysfs_pathname(parent, path);
strlcat(path, "/", PATH_MAX);
strlcat(path, name, PATH_MAX);
}
buf = kzalloc(PATH_MAX, GFP_KERNEL);
if (buf)
path = kernfs_path(parent, buf, PATH_MAX);
WARN(1, KERN_WARNING "sysfs: cannot create duplicate filename '%s'\n",
path ? path : name);
WARN(1, KERN_WARNING "sysfs: cannot create duplicate filename '%s/%s'\n",
path, name);
kfree(path);
kfree(buf);
}
/**
@@ -122,9 +101,13 @@ void sysfs_remove_dir(struct kobject *kobj)
int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
const void *new_ns)
{
struct kernfs_node *parent = kobj->sd->parent;
struct kernfs_node *parent;
int ret;
return kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
parent = kernfs_get_parent(kobj->sd);
ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
kernfs_put(parent);
return ret;
}
int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
@@ -133,7 +116,6 @@ int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
struct kernfs_node *kn = kobj->sd;
struct kernfs_node *new_parent;
BUG_ON(!kn->parent);
new_parent = new_parent_kobj && new_parent_kobj->sd ?
new_parent_kobj->sd : sysfs_root_kn;