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 BUG_ON(!old_ns); 85 get_uts_ns(old_ns); 86 87 if (!(flags & CLONE_NEWUTS)) 88 return old_ns; 89 90 new_ns = clone_uts_ns(user_ns, old_ns); 91 92 put_uts_ns(old_ns); 93 return new_ns; 94 } 95 96 void free_uts_ns(struct uts_namespace *ns) 97 { 98 ns_tree_remove(ns); 99 dec_uts_namespaces(ns->ucounts); 100 put_user_ns(ns->user_ns); 101 ns_common_free(ns); 102 /* Concurrent nstree traversal depends on a grace period. */ 103 kfree_rcu(ns, ns.ns_rcu); 104 } 105 106 static struct ns_common *utsns_get(struct task_struct *task) 107 { 108 struct uts_namespace *ns = NULL; 109 struct nsproxy *nsproxy; 110 111 task_lock(task); 112 nsproxy = task->nsproxy; 113 if (nsproxy) { 114 ns = nsproxy->uts_ns; 115 get_uts_ns(ns); 116 } 117 task_unlock(task); 118 119 return ns ? &ns->ns : NULL; 120 } 121 122 static void utsns_put(struct ns_common *ns) 123 { 124 put_uts_ns(to_uts_ns(ns)); 125 } 126 127 static int utsns_install(struct nsset *nsset, struct ns_common *new) 128 { 129 struct nsproxy *nsproxy = nsset->nsproxy; 130 struct uts_namespace *ns = to_uts_ns(new); 131 132 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || 133 !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN)) 134 return -EPERM; 135 136 get_uts_ns(ns); 137 put_uts_ns(nsproxy->uts_ns); 138 nsproxy->uts_ns = ns; 139 return 0; 140 } 141 142 static struct user_namespace *utsns_owner(struct ns_common *ns) 143 { 144 return to_uts_ns(ns)->user_ns; 145 } 146 147 const struct proc_ns_operations utsns_operations = { 148 .name = "uts", 149 .get = utsns_get, 150 .put = utsns_put, 151 .install = utsns_install, 152 .owner = utsns_owner, 153 }; 154 155 void __init uts_ns_init(void) 156 { 157 uts_ns_cache = kmem_cache_create_usercopy( 158 "uts_namespace", sizeof(struct uts_namespace), 0, 159 SLAB_PANIC|SLAB_ACCOUNT, 160 offsetof(struct uts_namespace, name), 161 sizeof_field(struct uts_namespace, name), 162 NULL); 163 ns_tree_add(&init_uts_ns); 164 } 165