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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 | // SPDX-License-Identifier: GPL-2.0-only /* * 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> */ #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 * * Return: 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|0777, 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; struct kernfs_root *root = kernfs_root(parent); int error; down_read(&root->kernfs_rwsem); error = kernfs_get_target_path(parent, target, path); up_read(&root->kernfs_rwsem); 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, }; |