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