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kernel/user_namespace.c
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/* * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation, version 2 of the * License. */ |
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#include <linux/export.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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static struct kmem_cache *user_ns_cachep __read_mostly; |
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/* |
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* Create a new user namespace, deriving the creator from the user in the * passed credentials, and replacing that user with the new root user for the * new namespace. * * This is called by copy_creds(), which will finish setting the target task's * credentials. |
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*/ |
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int create_user_ns(struct cred *new) |
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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 = kmem_cache_alloc(user_ns_cachep, GFP_KERNEL); |
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if (!ns) |
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return -ENOMEM; |
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kref_init(&ns->kref); 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. */ root_user = alloc_uid(ns, 0); if (!root_user) { |
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kmem_cache_free(user_ns_cachep, 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 */ ns->creator = new->user; new->user = root_user; new->uid = new->euid = new->suid = new->fsuid = 0; new->gid = new->egid = new->sgid = new->fsgid = 0; put_group_info(new->group_info); new->group_info = get_group_info(&init_groups); #ifdef CONFIG_KEYS key_put(new->request_key_auth); new->request_key_auth = NULL; #endif /* 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 */ put_user_ns(ns); |
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return 0; |
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} |
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/* * Deferred destructor for a user namespace. This is required because * free_user_ns() may be called with uidhash_lock held, but we need to call * back to free_uid() which will want to take the lock again. */ static void free_user_ns_work(struct work_struct *work) |
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{ |
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struct user_namespace *ns = container_of(work, struct user_namespace, destroyer); |
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free_uid(ns->creator); |
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kmem_cache_free(user_ns_cachep, ns); |
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} |
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void free_user_ns(struct kref *kref) { struct user_namespace *ns = container_of(kref, struct user_namespace, kref); INIT_WORK(&ns->destroyer, free_user_ns_work); schedule_work(&ns->destroyer); } |
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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) { struct user_namespace *tmp; if (likely(to == cred->user->user_ns)) return uid; /* Is cred->user the creator of the target user_ns * or the creator of one of it's parents? */ for ( tmp = to; tmp != &init_user_ns; tmp = tmp->creator->user_ns ) { if (cred->user == tmp->creator) { return (uid_t)0; } } /* No useful relationship so no mapping */ return overflowuid; } gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid) { struct user_namespace *tmp; if (likely(to == cred->user->user_ns)) return gid; /* Is cred->user the creator of the target user_ns * or the creator of one of it's parents? */ for ( tmp = to; tmp != &init_user_ns; tmp = tmp->creator->user_ns ) { if (cred->user == tmp->creator) { return (gid_t)0; } } /* No useful relationship so no mapping */ return overflowgid; } |
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static __init int user_namespaces_init(void) { user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC); return 0; } module_init(user_namespaces_init); |