1 /* 2 * Copyright (C) 2004 IBM Corporation 3 * 4 * Author: Serge Hallyn <serue@us.ibm.com> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License as 8 * published by the Free Software Foundation, version 2 of the 9 * License. 10 */ 11 12 #include <linux/export.h> 13 #include <linux/uts.h> 14 #include <linux/utsname.h> 15 #include <linux/err.h> 16 #include <linux/slab.h> 17 #include <linux/cred.h> 18 #include <linux/user_namespace.h> 19 #include <linux/proc_ns.h> 20 #include <linux/sched/task.h> 21 22 static struct kmem_cache *uts_ns_cache __ro_after_init; 23 24 static struct ucounts *inc_uts_namespaces(struct user_namespace *ns) 25 { 26 return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES); 27 } 28 29 static void dec_uts_namespaces(struct ucounts *ucounts) 30 { 31 dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES); 32 } 33 34 static struct uts_namespace *create_uts_ns(void) 35 { 36 struct uts_namespace *uts_ns; 37 38 uts_ns = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL); 39 if (uts_ns) 40 kref_init(&uts_ns->kref); 41 return uts_ns; 42 } 43 44 /* 45 * Clone a new ns copying an original utsname, setting refcount to 1 46 * @old_ns: namespace to clone 47 * Return ERR_PTR(-ENOMEM) on error (failure to allocate), new ns otherwise 48 */ 49 static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns, 50 struct uts_namespace *old_ns) 51 { 52 struct uts_namespace *ns; 53 struct ucounts *ucounts; 54 int err; 55 56 err = -ENOSPC; 57 ucounts = inc_uts_namespaces(user_ns); 58 if (!ucounts) 59 goto fail; 60 61 err = -ENOMEM; 62 ns = create_uts_ns(); 63 if (!ns) 64 goto fail_dec; 65 66 err = ns_alloc_inum(&ns->ns); 67 if (err) 68 goto fail_free; 69 70 ns->ucounts = ucounts; 71 ns->ns.ops = &utsns_operations; 72 73 down_read(&uts_sem); 74 memcpy(&ns->name, &old_ns->name, sizeof(ns->name)); 75 ns->user_ns = get_user_ns(user_ns); 76 up_read(&uts_sem); 77 return ns; 78 79 fail_free: 80 kmem_cache_free(uts_ns_cache, ns); 81 fail_dec: 82 dec_uts_namespaces(ucounts); 83 fail: 84 return ERR_PTR(err); 85 } 86 87 /* 88 * Copy task tsk's utsname namespace, or clone it if flags 89 * specifies CLONE_NEWUTS. In latter case, changes to the 90 * utsname of this process won't be seen by parent, and vice 91 * versa. 92 */ 93 struct uts_namespace *copy_utsname(unsigned long flags, 94 struct user_namespace *user_ns, struct uts_namespace *old_ns) 95 { 96 struct uts_namespace *new_ns; 97 98 BUG_ON(!old_ns); 99 get_uts_ns(old_ns); 100 101 if (!(flags & CLONE_NEWUTS)) 102 return old_ns; 103 104 new_ns = clone_uts_ns(user_ns, old_ns); 105 106 put_uts_ns(old_ns); 107 return new_ns; 108 } 109 110 void free_uts_ns(struct kref *kref) 111 { 112 struct uts_namespace *ns; 113 114 ns = container_of(kref, struct uts_namespace, kref); 115 dec_uts_namespaces(ns->ucounts); 116 put_user_ns(ns->user_ns); 117 ns_free_inum(&ns->ns); 118 kmem_cache_free(uts_ns_cache, ns); 119 } 120 121 static inline struct uts_namespace *to_uts_ns(struct ns_common *ns) 122 { 123 return container_of(ns, struct uts_namespace, ns); 124 } 125 126 static struct ns_common *utsns_get(struct task_struct *task) 127 { 128 struct uts_namespace *ns = NULL; 129 struct nsproxy *nsproxy; 130 131 task_lock(task); 132 nsproxy = task->nsproxy; 133 if (nsproxy) { 134 ns = nsproxy->uts_ns; 135 get_uts_ns(ns); 136 } 137 task_unlock(task); 138 139 return ns ? &ns->ns : NULL; 140 } 141 142 static void utsns_put(struct ns_common *ns) 143 { 144 put_uts_ns(to_uts_ns(ns)); 145 } 146 147 static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new) 148 { 149 struct uts_namespace *ns = to_uts_ns(new); 150 151 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || 152 !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) 153 return -EPERM; 154 155 get_uts_ns(ns); 156 put_uts_ns(nsproxy->uts_ns); 157 nsproxy->uts_ns = ns; 158 return 0; 159 } 160 161 static struct user_namespace *utsns_owner(struct ns_common *ns) 162 { 163 return to_uts_ns(ns)->user_ns; 164 } 165 166 const struct proc_ns_operations utsns_operations = { 167 .name = "uts", 168 .type = CLONE_NEWUTS, 169 .get = utsns_get, 170 .put = utsns_put, 171 .install = utsns_install, 172 .owner = utsns_owner, 173 }; 174 175 void __init uts_ns_init(void) 176 { 177 uts_ns_cache = kmem_cache_create_usercopy( 178 "uts_namespace", sizeof(struct uts_namespace), 0, 179 SLAB_PANIC|SLAB_ACCOUNT, 180 offsetof(struct uts_namespace, name), 181 sizeof_field(struct uts_namespace, name), 182 NULL); 183 } 184