1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2004 IBM Corporation 4 * 5 * Author: Serge Hallyn <serue@us.ibm.com> 6 */ 7 8 #include <linux/export.h> 9 #include <linux/uts.h> 10 #include <linux/utsname.h> 11 #include <linux/err.h> 12 #include <linux/slab.h> 13 #include <linux/cred.h> 14 #include <linux/user_namespace.h> 15 #include <linux/proc_ns.h> 16 #include <linux/nstree.h> 17 #include <linux/sched/task.h> 18 19 static struct kmem_cache *uts_ns_cache __ro_after_init; 20 21 static struct ucounts *inc_uts_namespaces(struct user_namespace *ns) 22 { 23 return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES); 24 } 25 26 static void dec_uts_namespaces(struct ucounts *ucounts) 27 { 28 dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES); 29 } 30 31 /* 32 * Clone a new ns copying an original utsname, setting refcount to 1 33 * @old_ns: namespace to clone 34 * Return ERR_PTR(-ENOMEM) on error (failure to allocate), new ns otherwise 35 */ 36 static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns, 37 struct uts_namespace *old_ns) 38 { 39 struct uts_namespace *ns; 40 struct ucounts *ucounts; 41 int err; 42 43 err = -ENOSPC; 44 ucounts = inc_uts_namespaces(user_ns); 45 if (!ucounts) 46 goto fail; 47 48 err = -ENOMEM; 49 ns = kmem_cache_zalloc(uts_ns_cache, GFP_KERNEL); 50 if (!ns) 51 goto fail_dec; 52 53 err = ns_common_init(ns); 54 if (err) 55 goto fail_free; 56 57 ns->ucounts = ucounts; 58 down_read(&uts_sem); 59 memcpy(&ns->name, &old_ns->name, sizeof(ns->name)); 60 ns->user_ns = get_user_ns(user_ns); 61 up_read(&uts_sem); 62 ns_tree_add(ns); 63 return ns; 64 65 fail_free: 66 kmem_cache_free(uts_ns_cache, ns); 67 fail_dec: 68 dec_uts_namespaces(ucounts); 69 fail: 70 return ERR_PTR(err); 71 } 72 73 /* 74 * Copy task tsk's utsname namespace, or clone it if flags 75 * specifies CLONE_NEWUTS. In latter case, changes to the 76 * utsname of this process won't be seen by parent, and vice 77 * versa. 78 */ 79 struct uts_namespace *copy_utsname(u64 flags, 80 struct user_namespace *user_ns, struct uts_namespace *old_ns) 81 { 82 struct uts_namespace *new_ns; 83 84 get_uts_ns(old_ns); 85 86 if (!(flags & CLONE_NEWUTS)) 87 return old_ns; 88 89 new_ns = clone_uts_ns(user_ns, old_ns); 90 91 put_uts_ns(old_ns); 92 return new_ns; 93 } 94 95 void free_uts_ns(struct uts_namespace *ns) 96 { 97 ns_tree_remove(ns); 98 dec_uts_namespaces(ns->ucounts); 99 put_user_ns(ns->user_ns); 100 ns_common_free(ns); 101 /* Concurrent nstree traversal depends on a grace period. */ 102 kfree_rcu(ns, ns.ns_rcu); 103 } 104 105 static struct ns_common *utsns_get(struct task_struct *task) 106 { 107 struct uts_namespace *ns = NULL; 108 struct nsproxy *nsproxy; 109 110 task_lock(task); 111 nsproxy = task->nsproxy; 112 if (nsproxy) { 113 ns = nsproxy->uts_ns; 114 get_uts_ns(ns); 115 } 116 task_unlock(task); 117 118 return ns ? &ns->ns : NULL; 119 } 120 121 static void utsns_put(struct ns_common *ns) 122 { 123 put_uts_ns(to_uts_ns(ns)); 124 } 125 126 static int utsns_install(struct nsset *nsset, struct ns_common *new) 127 { 128 struct nsproxy *nsproxy = nsset->nsproxy; 129 struct uts_namespace *ns = to_uts_ns(new); 130 131 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || 132 !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN)) 133 return -EPERM; 134 135 get_uts_ns(ns); 136 put_uts_ns(nsproxy->uts_ns); 137 nsproxy->uts_ns = ns; 138 return 0; 139 } 140 141 static struct user_namespace *utsns_owner(struct ns_common *ns) 142 { 143 return to_uts_ns(ns)->user_ns; 144 } 145 146 const struct proc_ns_operations utsns_operations = { 147 .name = "uts", 148 .get = utsns_get, 149 .put = utsns_put, 150 .install = utsns_install, 151 .owner = utsns_owner, 152 }; 153 154 void __init uts_ns_init(void) 155 { 156 uts_ns_cache = kmem_cache_create_usercopy( 157 "uts_namespace", sizeof(struct uts_namespace), 0, 158 SLAB_PANIC|SLAB_ACCOUNT, 159 offsetof(struct uts_namespace, name), 160 sizeof_field(struct uts_namespace, name), 161 NULL); 162 ns_tree_add(&init_uts_ns); 163 } 164