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153 lines
3.3 KiB
153 lines
3.3 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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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 <[email protected]> |
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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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* Ownership of the link matches ownership of the target. |
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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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kuid_t uid = GLOBAL_ROOT_UID; |
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kgid_t gid = GLOBAL_ROOT_GID; |
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if (target->iattr) { |
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uid = target->iattr->ia_uid; |
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gid = target->iattr->ia_gid; |
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} |
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kn = kernfs_new_node(parent, name, S_IFLNK|S_IRWXUGO, uid, gid, |
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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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if ((s - path) + 3 >= PATH_MAX) |
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return -ENAMETOOLONG; |
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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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memcpy(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 inode *inode, char *path) |
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{ |
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struct kernfs_node *kn = inode->i_private; |
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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_get_link(struct dentry *dentry, |
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struct inode *inode, |
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struct delayed_call *done) |
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{ |
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char *body; |
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int error; |
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if (!dentry) |
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return ERR_PTR(-ECHILD); |
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body = kzalloc(PAGE_SIZE, GFP_KERNEL); |
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if (!body) |
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return ERR_PTR(-ENOMEM); |
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error = kernfs_getlink(inode, body); |
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if (unlikely(error < 0)) { |
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kfree(body); |
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return ERR_PTR(error); |
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} |
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set_delayed_call(done, kfree_link, body); |
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return body; |
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} |
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const struct inode_operations kernfs_symlink_iops = { |
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.listxattr = kernfs_iop_listxattr, |
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.get_link = kernfs_iop_get_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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