680baacbca
a) instead of storing the symlink body (via nd_set_link()) and returning an opaque pointer later passed to ->put_link(), ->follow_link() _stores_ that opaque pointer (into void * passed by address by caller) and returns the symlink body. Returning ERR_PTR() on error, NULL on jump (procfs magic symlinks) and pointer to symlink body for normal symlinks. Stored pointer is ignored in all cases except the last one. Storing NULL for opaque pointer (or not storing it at all) means no call of ->put_link(). b) the body used to be passed to ->put_link() implicitly (via nameidata). Now only the opaque pointer is. In the cases when we used the symlink body to free stuff, ->follow_link() now should store it as opaque pointer in addition to returning it. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
146 lines
3.3 KiB
C
146 lines
3.3 KiB
C
/*
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* fs/kernfs/symlink.c - kernfs symlink 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, 2013 Tejun Heo <tj@kernel.org>
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*
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* This file is released under the GPLv2.
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*/
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#include <linux/fs.h>
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#include <linux/gfp.h>
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#include <linux/namei.h>
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#include "kernfs-internal.h"
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/**
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* kernfs_create_link - create a symlink
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* @parent: directory to create the symlink in
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* @name: name of the symlink
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* @target: target node for the symlink to point to
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*
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* Returns the created node on success, ERR_PTR() value on error.
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*/
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struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
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const char *name,
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struct kernfs_node *target)
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{
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struct kernfs_node *kn;
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int error;
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kn = kernfs_new_node(parent, name, S_IFLNK|S_IRWXUGO, KERNFS_LINK);
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if (!kn)
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return ERR_PTR(-ENOMEM);
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if (kernfs_ns_enabled(parent))
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kn->ns = target->ns;
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kn->symlink.target_kn = target;
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kernfs_get(target); /* ref owned by symlink */
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error = kernfs_add_one(kn);
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if (!error)
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return kn;
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kernfs_put(kn);
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return ERR_PTR(error);
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}
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static int kernfs_get_target_path(struct kernfs_node *parent,
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struct kernfs_node *target, char *path)
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{
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struct kernfs_node *base, *kn;
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char *s = path;
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int len = 0;
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/* go up to the root, stop at the base */
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base = parent;
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while (base->parent) {
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kn = target->parent;
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while (kn->parent && base != kn)
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kn = kn->parent;
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if (base == kn)
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break;
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strcpy(s, "../");
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s += 3;
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base = base->parent;
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}
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/* determine end of target string for reverse fillup */
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kn = target;
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while (kn->parent && kn != base) {
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len += strlen(kn->name) + 1;
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kn = kn->parent;
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}
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/* check limits */
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if (len < 2)
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return -EINVAL;
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len--;
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if ((s - path) + len > PATH_MAX)
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return -ENAMETOOLONG;
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/* reverse fillup of target string from target to base */
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kn = target;
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while (kn->parent && kn != base) {
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int slen = strlen(kn->name);
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len -= slen;
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strncpy(s + len, kn->name, slen);
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if (len)
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s[--len] = '/';
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kn = kn->parent;
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}
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return 0;
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}
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static int kernfs_getlink(struct dentry *dentry, char *path)
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{
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struct kernfs_node *kn = dentry->d_fsdata;
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struct kernfs_node *parent = kn->parent;
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struct kernfs_node *target = kn->symlink.target_kn;
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int error;
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mutex_lock(&kernfs_mutex);
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error = kernfs_get_target_path(parent, target, path);
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mutex_unlock(&kernfs_mutex);
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return error;
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}
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static const char *kernfs_iop_follow_link(struct dentry *dentry, void **cookie, struct nameidata *nd)
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{
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int error = -ENOMEM;
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unsigned long page = get_zeroed_page(GFP_KERNEL);
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if (!page)
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return ERR_PTR(-ENOMEM);
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error = kernfs_getlink(dentry, (char *)page);
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if (unlikely(error < 0)) {
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free_page((unsigned long)page);
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return ERR_PTR(error);
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}
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return *cookie = (char *)page;
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}
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static void kernfs_iop_put_link(struct dentry *dentry, void *cookie)
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{
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free_page((unsigned long)cookie);
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}
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const struct inode_operations kernfs_symlink_iops = {
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.setxattr = kernfs_iop_setxattr,
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.removexattr = kernfs_iop_removexattr,
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.getxattr = kernfs_iop_getxattr,
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.listxattr = kernfs_iop_listxattr,
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.readlink = generic_readlink,
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.follow_link = kernfs_iop_follow_link,
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.put_link = kernfs_iop_put_link,
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.setattr = kernfs_iop_setattr,
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.getattr = kernfs_iop_getattr,
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.permission = kernfs_iop_permission,
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};
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