5c1469de75
Define what happens when a we view a uid from one user_namespace in another user_namepece. - If the user namespaces are the same no mapping is necessary. - For most cases of difference use overflowuid and overflowgid, the uid and gid currently used for 16bit apis when we have a 32bit uid that does fit in 16bits. Effectively the situation is the same, we want to return a uid or gid that is not assigned to any user. - For the case when we happen to be mapping the uid or gid of the creator of the target user namespace use uid 0 and gid as confusing that user with root is not a problem. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Acked-by: Serge E. Hallyn <serue@us.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
128 lines
3.2 KiB
C
128 lines
3.2 KiB
C
/*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*/
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#include <linux/module.h>
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#include <linux/nsproxy.h>
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#include <linux/slab.h>
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#include <linux/user_namespace.h>
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#include <linux/highuid.h>
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#include <linux/cred.h>
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/*
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* Create a new user namespace, deriving the creator from the user in the
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* passed credentials, and replacing that user with the new root user for the
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* new namespace.
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*
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* This is called by copy_creds(), which will finish setting the target task's
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* credentials.
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*/
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int create_user_ns(struct cred *new)
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{
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struct user_namespace *ns;
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struct user_struct *root_user;
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int n;
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ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
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if (!ns)
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return -ENOMEM;
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kref_init(&ns->kref);
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for (n = 0; n < UIDHASH_SZ; ++n)
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INIT_HLIST_HEAD(ns->uidhash_table + n);
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/* Alloc new root user. */
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root_user = alloc_uid(ns, 0);
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if (!root_user) {
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kfree(ns);
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return -ENOMEM;
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}
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/* set the new root user in the credentials under preparation */
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ns->creator = new->user;
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new->user = root_user;
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new->uid = new->euid = new->suid = new->fsuid = 0;
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new->gid = new->egid = new->sgid = new->fsgid = 0;
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put_group_info(new->group_info);
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new->group_info = get_group_info(&init_groups);
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#ifdef CONFIG_KEYS
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key_put(new->request_key_auth);
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new->request_key_auth = NULL;
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#endif
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/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
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/* root_user holds a reference to ns, our reference can be dropped */
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put_user_ns(ns);
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return 0;
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}
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/*
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* Deferred destructor for a user namespace. This is required because
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* free_user_ns() may be called with uidhash_lock held, but we need to call
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* back to free_uid() which will want to take the lock again.
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*/
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static void free_user_ns_work(struct work_struct *work)
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{
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struct user_namespace *ns =
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container_of(work, struct user_namespace, destroyer);
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free_uid(ns->creator);
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kfree(ns);
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}
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void free_user_ns(struct kref *kref)
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{
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struct user_namespace *ns =
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container_of(kref, struct user_namespace, kref);
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INIT_WORK(&ns->destroyer, free_user_ns_work);
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schedule_work(&ns->destroyer);
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}
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EXPORT_SYMBOL(free_user_ns);
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uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid)
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{
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struct user_namespace *tmp;
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if (likely(to == cred->user->user_ns))
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return uid;
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/* Is cred->user the creator of the target user_ns
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* or the creator of one of it's parents?
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*/
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for ( tmp = to; tmp != &init_user_ns;
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tmp = tmp->creator->user_ns ) {
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if (cred->user == tmp->creator) {
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return (uid_t)0;
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}
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}
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/* No useful relationship so no mapping */
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return overflowuid;
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}
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gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid)
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{
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struct user_namespace *tmp;
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if (likely(to == cred->user->user_ns))
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return gid;
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/* Is cred->user the creator of the target user_ns
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* or the creator of one of it's parents?
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*/
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for ( tmp = to; tmp != &init_user_ns;
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tmp = tmp->creator->user_ns ) {
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if (cred->user == tmp->creator) {
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return (gid_t)0;
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}
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}
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/* No useful relationship so no mapping */
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return overflowgid;
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}
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