linux/fs/kernfs/symlink.c
Ondrej Mosnacek 0589521962 kernfs: clean up struct kernfs_iattrs
Right now, kernfs_iattrs embeds the whole struct iattr, even though it
doesn't really use half of its fields... This both leads to wasting
space and makes the code look awkward. Let's just list the few fields
we need directly in struct kernfs_iattrs.

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
[PM: merged a number of chunks manually due to fuzz]
Signed-off-by: Paul Moore <paul@paul-moore.com>
2019-03-20 21:42:14 -04:00

155 lines
3.3 KiB
C

/*
* fs/kernfs/symlink.c - kernfs symlink implementation
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
*
* This file is released under the GPLv2.
*/
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/namei.h>
#include "kernfs-internal.h"
/**
* kernfs_create_link - create a symlink
* @parent: directory to create the symlink in
* @name: name of the symlink
* @target: target node for the symlink to point to
*
* Returns the created node on success, ERR_PTR() value on error.
* Ownership of the link matches ownership of the target.
*/
struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
const char *name,
struct kernfs_node *target)
{
struct kernfs_node *kn;
int error;
kuid_t uid = GLOBAL_ROOT_UID;
kgid_t gid = GLOBAL_ROOT_GID;
if (target->iattr) {
uid = target->iattr->ia_uid;
gid = target->iattr->ia_gid;
}
kn = kernfs_new_node(parent, name, S_IFLNK|S_IRWXUGO, uid, gid,
KERNFS_LINK);
if (!kn)
return ERR_PTR(-ENOMEM);
if (kernfs_ns_enabled(parent))
kn->ns = target->ns;
kn->symlink.target_kn = target;
kernfs_get(target); /* ref owned by symlink */
error = kernfs_add_one(kn);
if (!error)
return kn;
kernfs_put(kn);
return ERR_PTR(error);
}
static int kernfs_get_target_path(struct kernfs_node *parent,
struct kernfs_node *target, char *path)
{
struct kernfs_node *base, *kn;
char *s = path;
int len = 0;
/* go up to the root, stop at the base */
base = parent;
while (base->parent) {
kn = target->parent;
while (kn->parent && base != kn)
kn = kn->parent;
if (base == kn)
break;
if ((s - path) + 3 >= PATH_MAX)
return -ENAMETOOLONG;
strcpy(s, "../");
s += 3;
base = base->parent;
}
/* determine end of target string for reverse fillup */
kn = target;
while (kn->parent && kn != base) {
len += strlen(kn->name) + 1;
kn = kn->parent;
}
/* check limits */
if (len < 2)
return -EINVAL;
len--;
if ((s - path) + len >= PATH_MAX)
return -ENAMETOOLONG;
/* reverse fillup of target string from target to base */
kn = target;
while (kn->parent && kn != base) {
int slen = strlen(kn->name);
len -= slen;
memcpy(s + len, kn->name, slen);
if (len)
s[--len] = '/';
kn = kn->parent;
}
return 0;
}
static int kernfs_getlink(struct inode *inode, char *path)
{
struct kernfs_node *kn = inode->i_private;
struct kernfs_node *parent = kn->parent;
struct kernfs_node *target = kn->symlink.target_kn;
int error;
mutex_lock(&kernfs_mutex);
error = kernfs_get_target_path(parent, target, path);
mutex_unlock(&kernfs_mutex);
return error;
}
static const char *kernfs_iop_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
char *body;
int error;
if (!dentry)
return ERR_PTR(-ECHILD);
body = kzalloc(PAGE_SIZE, GFP_KERNEL);
if (!body)
return ERR_PTR(-ENOMEM);
error = kernfs_getlink(inode, body);
if (unlikely(error < 0)) {
kfree(body);
return ERR_PTR(error);
}
set_delayed_call(done, kfree_link, body);
return body;
}
const struct inode_operations kernfs_symlink_iops = {
.listxattr = kernfs_iop_listxattr,
.get_link = kernfs_iop_get_link,
.setattr = kernfs_iop_setattr,
.getattr = kernfs_iop_getattr,
.permission = kernfs_iop_permission,
};