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Commit db4aad20 authored by Tejun Heo's avatar Tejun Heo Committed by Greg Kroah-Hartman
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kernfs: associate a new kernfs_node with its parent on creation 



Once created, a kernfs_node is always destroyed by kernfs_put().
Since ba7443bc ("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: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 917f56ca

fs/kernfs/dir.c

+26 −14
Original line number Diff line number Diff line
@@ -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)

fs/kernfs/file.c

+2 −3
Original line number Diff line number Diff line
@@ -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) {

fs/kernfs/kernfs-internal.h

+4 −4
Original line number Diff line number Diff line
@@ -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

fs/kernfs/symlink.c

+2 −3
Original line number Diff line number Diff line
@@ -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)