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3eef34ad7d
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>
124 lines
3.1 KiB
C
124 lines
3.1 KiB
C
/*
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* fs/sysfs/dir.c - sysfs core and dir operation implementation
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*
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* Copyright (c) 2001-3 Patrick Mochel
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* Copyright (c) 2007 SUSE Linux Products GmbH
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* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
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*
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* This file is released under the GPLv2.
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*
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* Please see Documentation/filesystems/sysfs.txt for more information.
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*/
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#undef DEBUG
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#include <linux/fs.h>
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#include <linux/kobject.h>
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#include <linux/slab.h>
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#include "sysfs.h"
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DEFINE_SPINLOCK(sysfs_symlink_target_lock);
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void sysfs_warn_dup(struct kernfs_node *parent, const char *name)
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{
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char *buf, *path = NULL;
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buf = kzalloc(PATH_MAX, GFP_KERNEL);
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if (buf)
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path = kernfs_path(parent, buf, PATH_MAX);
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WARN(1, KERN_WARNING "sysfs: cannot create duplicate filename '%s/%s'\n",
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path, name);
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kfree(buf);
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}
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/**
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* sysfs_create_dir_ns - create a directory for an object with a namespace tag
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* @kobj: object we're creating directory for
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* @ns: the namespace tag to use
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*/
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int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
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{
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struct kernfs_node *parent, *kn;
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BUG_ON(!kobj);
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if (kobj->parent)
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parent = kobj->parent->sd;
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else
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parent = sysfs_root_kn;
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if (!parent)
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return -ENOENT;
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kn = kernfs_create_dir_ns(parent, kobject_name(kobj),
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S_IRWXU | S_IRUGO | S_IXUGO, kobj, ns);
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if (IS_ERR(kn)) {
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if (PTR_ERR(kn) == -EEXIST)
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sysfs_warn_dup(parent, kobject_name(kobj));
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return PTR_ERR(kn);
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}
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kobj->sd = kn;
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return 0;
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}
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/**
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* sysfs_remove_dir - remove an object's directory.
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* @kobj: object.
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*
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* The only thing special about this is that we remove any files in
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* the directory before we remove the directory, and we've inlined
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* what used to be sysfs_rmdir() below, instead of calling separately.
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*/
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void sysfs_remove_dir(struct kobject *kobj)
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{
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struct kernfs_node *kn = kobj->sd;
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/*
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* In general, kboject owner is responsible for ensuring removal
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* doesn't race with other operations and sysfs doesn't provide any
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* protection; however, when @kobj is used as a symlink target, the
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* symlinking entity usually doesn't own @kobj and thus has no
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* control over removal. @kobj->sd may be removed anytime
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* and symlink code may end up dereferencing an already freed node.
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*
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* sysfs_symlink_target_lock synchronizes @kobj->sd
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* disassociation against symlink operations so that symlink code
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* can safely dereference @kobj->sd.
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*/
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spin_lock(&sysfs_symlink_target_lock);
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kobj->sd = NULL;
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spin_unlock(&sysfs_symlink_target_lock);
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if (kn) {
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WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
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kernfs_remove(kn);
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}
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}
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int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
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const void *new_ns)
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{
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struct kernfs_node *parent;
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int ret;
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parent = kernfs_get_parent(kobj->sd);
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ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
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kernfs_put(parent);
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return ret;
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}
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int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
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const void *new_ns)
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{
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struct kernfs_node *kn = kobj->sd;
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struct kernfs_node *new_parent;
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new_parent = new_parent_kobj && new_parent_kobj->sd ?
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new_parent_kobj->sd : sysfs_root_kn;
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return kernfs_rename_ns(kn, new_parent, kn->name, new_ns);
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}
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