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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 = proc_alloc_inum(&ns->proc_inum);
 46         if (err) {
 47                 kfree(ns);
 48                 return ERR_PTR(err);
 49         }
 50 
 51         down_read(&uts_sem);
 52         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
 53         ns->user_ns = get_user_ns(user_ns);
 54         up_read(&uts_sem);
 55         return ns;
 56 }
 57 
 58 /*
 59  * Copy task tsk's utsname namespace, or clone it if flags
 60  * specifies CLONE_NEWUTS.  In latter case, changes to the
 61  * utsname of this process won't be seen by parent, and vice
 62  * versa.
 63  */
 64 struct uts_namespace *copy_utsname(unsigned long flags,
 65         struct user_namespace *user_ns, struct uts_namespace *old_ns)
 66 {
 67         struct uts_namespace *new_ns;
 68 
 69         BUG_ON(!old_ns);
 70         get_uts_ns(old_ns);
 71 
 72         if (!(flags & CLONE_NEWUTS))
 73                 return old_ns;
 74 
 75         new_ns = clone_uts_ns(user_ns, old_ns);
 76 
 77         put_uts_ns(old_ns);
 78         return new_ns;
 79 }
 80 
 81 void free_uts_ns(struct kref *kref)
 82 {
 83         struct uts_namespace *ns;
 84 
 85         ns = container_of(kref, struct uts_namespace, kref);
 86         put_user_ns(ns->user_ns);
 87         proc_free_inum(ns->proc_inum);
 88         kfree(ns);
 89 }
 90 
 91 static void *utsns_get(struct task_struct *task)
 92 {
 93         struct uts_namespace *ns = NULL;
 94         struct nsproxy *nsproxy;
 95 
 96         rcu_read_lock();
 97         nsproxy = task_nsproxy(task);
 98         if (nsproxy) {
 99                 ns = nsproxy->uts_ns;
100                 get_uts_ns(ns);
101         }
102         rcu_read_unlock();
103 
104         return ns;
105 }
106 
107 static void utsns_put(void *ns)
108 {
109         put_uts_ns(ns);
110 }
111 
112 static int utsns_install(struct nsproxy *nsproxy, void *new)
113 {
114         struct uts_namespace *ns = new;
115 
116         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
117             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
118                 return -EPERM;
119 
120         get_uts_ns(ns);
121         put_uts_ns(nsproxy->uts_ns);
122         nsproxy->uts_ns = ns;
123         return 0;
124 }
125 
126 static unsigned int utsns_inum(void *vp)
127 {
128         struct uts_namespace *ns = vp;
129 
130         return ns->proc_inum;
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         .inum           = utsns_inum,
140 };
141 

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