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Linux/kernel/utsname.c

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  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/user_namespace.h>
 18 #include <linux/proc_ns.h>
 19 
 20 static struct uts_namespace *create_uts_ns(void)
 21 {
 22         struct uts_namespace *uts_ns;
 23 
 24         uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
 25         if (uts_ns)
 26                 kref_init(&uts_ns->kref);
 27         return uts_ns;
 28 }
 29 
 30 /*
 31  * Clone a new ns copying an original utsname, setting refcount to 1
 32  * @old_ns: namespace to clone
 33  * Return ERR_PTR(-ENOMEM) on error (failure to kmalloc), new ns otherwise
 34  */
 35 static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
 36                                           struct uts_namespace *old_ns)
 37 {
 38         struct uts_namespace *ns;
 39         int err;
 40 
 41         ns = create_uts_ns();
 42         if (!ns)
 43                 return ERR_PTR(-ENOMEM);
 44 
 45         err = ns_alloc_inum(&ns->ns);
 46         if (err) {
 47                 kfree(ns);
 48                 return ERR_PTR(err);
 49         }
 50 
 51         ns->ns.ops = &utsns_operations;
 52 
 53         down_read(&uts_sem);
 54         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
 55         ns->user_ns = get_user_ns(user_ns);
 56         up_read(&uts_sem);
 57         return ns;
 58 }
 59 
 60 /*
 61  * Copy task tsk's utsname namespace, or clone it if flags
 62  * specifies CLONE_NEWUTS.  In latter case, changes to the
 63  * utsname of this process won't be seen by parent, and vice
 64  * versa.
 65  */
 66 struct uts_namespace *copy_utsname(unsigned long flags,
 67         struct user_namespace *user_ns, struct uts_namespace *old_ns)
 68 {
 69         struct uts_namespace *new_ns;
 70 
 71         BUG_ON(!old_ns);
 72         get_uts_ns(old_ns);
 73 
 74         if (!(flags & CLONE_NEWUTS))
 75                 return old_ns;
 76 
 77         new_ns = clone_uts_ns(user_ns, old_ns);
 78 
 79         put_uts_ns(old_ns);
 80         return new_ns;
 81 }
 82 
 83 void free_uts_ns(struct kref *kref)
 84 {
 85         struct uts_namespace *ns;
 86 
 87         ns = container_of(kref, struct uts_namespace, kref);
 88         put_user_ns(ns->user_ns);
 89         ns_free_inum(&ns->ns);
 90         kfree(ns);
 91 }
 92 
 93 static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
 94 {
 95         return container_of(ns, struct uts_namespace, ns);
 96 }
 97 
 98 static struct ns_common *utsns_get(struct task_struct *task)
 99 {
100         struct uts_namespace *ns = NULL;
101         struct nsproxy *nsproxy;
102 
103         task_lock(task);
104         nsproxy = task->nsproxy;
105         if (nsproxy) {
106                 ns = nsproxy->uts_ns;
107                 get_uts_ns(ns);
108         }
109         task_unlock(task);
110 
111         return ns ? &ns->ns : NULL;
112 }
113 
114 static void utsns_put(struct ns_common *ns)
115 {
116         put_uts_ns(to_uts_ns(ns));
117 }
118 
119 static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new)
120 {
121         struct uts_namespace *ns = to_uts_ns(new);
122 
123         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
124             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
125                 return -EPERM;
126 
127         get_uts_ns(ns);
128         put_uts_ns(nsproxy->uts_ns);
129         nsproxy->uts_ns = ns;
130         return 0;
131 }
132 
133 const struct proc_ns_operations utsns_operations = {
134         .name           = "uts",
135         .type           = CLONE_NEWUTS,
136         .get            = utsns_get,
137         .put            = utsns_put,
138         .install        = utsns_install,
139 };
140 

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