kernfs: associate a new kernfs_node with its parent on creation

Once created, a kernfs_node is always destroyed by kernfs_put().
Since ba7443bc65 ("sysfs, kernfs: implement
kernfs_create/destroy_root()"), kernfs_put() depends on kernfs_root()
to locate the ino_ida.  kernfs_root() in turn depends on
kernfs_node->parent being set for !dir nodes.  This means that
kernfs_put() of a !dir node requires its ->parent to be initialized.

This leads to oops when a newly created !dir node is destroyed without
going through kernfs_add_one() or after failing kernfs_add_one()
before ->parent is set.  kernfs_root() invoked from kernfs_put() will
try to dereference NULL parent.

Fix it by moving parent association to kernfs_new_node() from
kernfs_add_one().  kernfs_new_node() now takes @parent instead of
@root and determines the root from the parent and also sets the new
node's parent properly.  @parent parameter is removed from
kernfs_add_one().  As there's no parent when creating the root node,
__kernfs_new_node() which takes @root as before and doesn't set the
parent is used in that case.

This ensures that a kernfs_node in any stage in its life has its
parent associated and thus can be put.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tejun Heo 2014-01-17 09:58:25 -05:00 committed by Greg Kroah-Hartman
parent 917f56caaa
commit db4aad209b
4 changed files with 34 additions and 24 deletions

View File

@ -324,8 +324,9 @@ const struct dentry_operations kernfs_dops = {
.d_release = kernfs_dop_release,
};
struct kernfs_node *kernfs_new_node(struct kernfs_root *root, const char *name,
umode_t mode, unsigned flags)
static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
const char *name, umode_t mode,
unsigned flags)
{
char *dup_name = NULL;
struct kernfs_node *kn;
@ -362,6 +363,20 @@ struct kernfs_node *kernfs_new_node(struct kernfs_root *root, const char *name,
return NULL;
}
struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
const char *name, umode_t mode,
unsigned flags)
{
struct kernfs_node *kn;
kn = __kernfs_new_node(kernfs_root(parent), name, mode, flags);
if (kn) {
kernfs_get(parent);
kn->parent = parent;
}
return kn;
}
/**
* kernfs_addrm_start - prepare for kernfs_node add/remove
* @acxt: pointer to kernfs_addrm_cxt to be used
@ -386,11 +401,10 @@ void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt)
* kernfs_add_one - add kernfs_node to parent without warning
* @acxt: addrm context to use
* @kn: kernfs_node to be added
* @parent: the parent kernfs_node to add @kn to
*
* Get @parent and set @kn->parent to it and increment nlink of the
* parent inode if @kn is a directory and link into the children list
* of the parent.
* The caller must already have initialized @kn->parent. This
* function increments nlink of the parent's inode if @kn is a
* directory and link into the children list of the parent.
*
* This function should be called between calls to
* kernfs_addrm_start() and kernfs_addrm_finish() and should be passed
@ -403,9 +417,9 @@ void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt)
* 0 on success, -EEXIST if entry with the given name already
* exists.
*/
int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn,
struct kernfs_node *parent)
int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn)
{
struct kernfs_node *parent = kn->parent;
bool has_ns = kernfs_ns_enabled(parent);
struct kernfs_iattrs *ps_iattr;
int ret;
@ -423,8 +437,6 @@ int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn,
return -ENOENT;
kn->hash = kernfs_name_hash(kn->name, kn->ns);
kn->parent = parent;
kernfs_get(parent);
ret = kernfs_link_sibling(kn);
if (ret)
@ -600,7 +612,8 @@ struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
ida_init(&root->ino_ida);
kn = kernfs_new_node(root, "", S_IFDIR | S_IRUGO | S_IXUGO, KERNFS_DIR);
kn = __kernfs_new_node(root, "", S_IFDIR | S_IRUGO | S_IXUGO,
KERNFS_DIR);
if (!kn) {
ida_destroy(&root->ino_ida);
kfree(root);
@ -648,8 +661,7 @@ struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
int rc;
/* allocate */
kn = kernfs_new_node(kernfs_root(parent), name, mode | S_IFDIR,
KERNFS_DIR);
kn = kernfs_new_node(parent, name, mode | S_IFDIR, KERNFS_DIR);
if (!kn)
return ERR_PTR(-ENOMEM);
@ -659,7 +671,7 @@ struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
/* link in */
kernfs_addrm_start(&acxt);
rc = kernfs_add_one(&acxt, kn, parent);
rc = kernfs_add_one(&acxt, kn);
kernfs_addrm_finish(&acxt);
if (!rc)

View File

@ -829,8 +829,7 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
if (name_is_static)
flags |= KERNFS_STATIC_NAME;
kn = kernfs_new_node(kernfs_root(parent), name,
(mode & S_IALLUGO) | S_IFREG, flags);
kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG, flags);
if (!kn)
return ERR_PTR(-ENOMEM);
@ -857,7 +856,7 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
kn->flags |= KERNFS_HAS_MMAP;
kernfs_addrm_start(&acxt);
rc = kernfs_add_one(&acxt, kn, parent);
rc = kernfs_add_one(&acxt, kn);
kernfs_addrm_finish(&acxt);
if (rc) {

View File

@ -101,11 +101,11 @@ extern const struct inode_operations kernfs_dir_iops;
struct kernfs_node *kernfs_get_active(struct kernfs_node *kn);
void kernfs_put_active(struct kernfs_node *kn);
void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt);
int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn,
struct kernfs_node *parent);
int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn);
void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt);
struct kernfs_node *kernfs_new_node(struct kernfs_root *root, const char *name,
umode_t mode, unsigned flags);
struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
const char *name, umode_t mode,
unsigned flags);
/*
* file.c

View File

@ -30,8 +30,7 @@ struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
struct kernfs_addrm_cxt acxt;
int error;
kn = kernfs_new_node(kernfs_root(parent), name, S_IFLNK|S_IRWXUGO,
KERNFS_LINK);
kn = kernfs_new_node(parent, name, S_IFLNK|S_IRWXUGO, KERNFS_LINK);
if (!kn)
return ERR_PTR(-ENOMEM);
@ -41,7 +40,7 @@ struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
kernfs_get(target); /* ref owned by symlink */
kernfs_addrm_start(&acxt);
error = kernfs_add_one(&acxt, kn, parent);
error = kernfs_add_one(&acxt, kn);
kernfs_addrm_finish(&acxt);
if (!error)