diff options
Diffstat (limited to '')
-rw-r--r-- | fs/kernfs/symlink.c | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c new file mode 100644 index 000000000..5432883d8 --- /dev/null +++ b/fs/kernfs/symlink.c @@ -0,0 +1,153 @@ +// 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 + * + * 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, +}; |