cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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symlink.c (3427B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * fs/kernfs/symlink.c - kernfs symlink implementation
      4 *
      5 * Copyright (c) 2001-3 Patrick Mochel
      6 * Copyright (c) 2007 SUSE Linux Products GmbH
      7 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
      8 */
      9
     10#include <linux/fs.h>
     11#include <linux/gfp.h>
     12#include <linux/namei.h>
     13
     14#include "kernfs-internal.h"
     15
     16/**
     17 * kernfs_create_link - create a symlink
     18 * @parent: directory to create the symlink in
     19 * @name: name of the symlink
     20 * @target: target node for the symlink to point to
     21 *
     22 * Returns the created node on success, ERR_PTR() value on error.
     23 * Ownership of the link matches ownership of the target.
     24 */
     25struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
     26				       const char *name,
     27				       struct kernfs_node *target)
     28{
     29	struct kernfs_node *kn;
     30	int error;
     31	kuid_t uid = GLOBAL_ROOT_UID;
     32	kgid_t gid = GLOBAL_ROOT_GID;
     33
     34	if (target->iattr) {
     35		uid = target->iattr->ia_uid;
     36		gid = target->iattr->ia_gid;
     37	}
     38
     39	kn = kernfs_new_node(parent, name, S_IFLNK|0777, uid, gid, KERNFS_LINK);
     40	if (!kn)
     41		return ERR_PTR(-ENOMEM);
     42
     43	if (kernfs_ns_enabled(parent))
     44		kn->ns = target->ns;
     45	kn->symlink.target_kn = target;
     46	kernfs_get(target);	/* ref owned by symlink */
     47
     48	error = kernfs_add_one(kn);
     49	if (!error)
     50		return kn;
     51
     52	kernfs_put(kn);
     53	return ERR_PTR(error);
     54}
     55
     56static int kernfs_get_target_path(struct kernfs_node *parent,
     57				  struct kernfs_node *target, char *path)
     58{
     59	struct kernfs_node *base, *kn;
     60	char *s = path;
     61	int len = 0;
     62
     63	/* go up to the root, stop at the base */
     64	base = parent;
     65	while (base->parent) {
     66		kn = target->parent;
     67		while (kn->parent && base != kn)
     68			kn = kn->parent;
     69
     70		if (base == kn)
     71			break;
     72
     73		if ((s - path) + 3 >= PATH_MAX)
     74			return -ENAMETOOLONG;
     75
     76		strcpy(s, "../");
     77		s += 3;
     78		base = base->parent;
     79	}
     80
     81	/* determine end of target string for reverse fillup */
     82	kn = target;
     83	while (kn->parent && kn != base) {
     84		len += strlen(kn->name) + 1;
     85		kn = kn->parent;
     86	}
     87
     88	/* check limits */
     89	if (len < 2)
     90		return -EINVAL;
     91	len--;
     92	if ((s - path) + len >= PATH_MAX)
     93		return -ENAMETOOLONG;
     94
     95	/* reverse fillup of target string from target to base */
     96	kn = target;
     97	while (kn->parent && kn != base) {
     98		int slen = strlen(kn->name);
     99
    100		len -= slen;
    101		memcpy(s + len, kn->name, slen);
    102		if (len)
    103			s[--len] = '/';
    104
    105		kn = kn->parent;
    106	}
    107
    108	return 0;
    109}
    110
    111static int kernfs_getlink(struct inode *inode, char *path)
    112{
    113	struct kernfs_node *kn = inode->i_private;
    114	struct kernfs_node *parent = kn->parent;
    115	struct kernfs_node *target = kn->symlink.target_kn;
    116	struct kernfs_root *root = kernfs_root(parent);
    117	int error;
    118
    119	down_read(&root->kernfs_rwsem);
    120	error = kernfs_get_target_path(parent, target, path);
    121	up_read(&root->kernfs_rwsem);
    122
    123	return error;
    124}
    125
    126static const char *kernfs_iop_get_link(struct dentry *dentry,
    127				       struct inode *inode,
    128				       struct delayed_call *done)
    129{
    130	char *body;
    131	int error;
    132
    133	if (!dentry)
    134		return ERR_PTR(-ECHILD);
    135	body = kzalloc(PAGE_SIZE, GFP_KERNEL);
    136	if (!body)
    137		return ERR_PTR(-ENOMEM);
    138	error = kernfs_getlink(inode, body);
    139	if (unlikely(error < 0)) {
    140		kfree(body);
    141		return ERR_PTR(error);
    142	}
    143	set_delayed_call(done, kfree_link, body);
    144	return body;
    145}
    146
    147const struct inode_operations kernfs_symlink_iops = {
    148	.listxattr	= kernfs_iop_listxattr,
    149	.get_link	= kernfs_iop_get_link,
    150	.setattr	= kernfs_iop_setattr,
    151	.getattr	= kernfs_iop_getattr,
    152	.permission	= kernfs_iop_permission,
    153};