1 /*
2 * Copyright (C) 2007
3 *
4 * Author: Eric Biederman <ebiederm@xmision.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/sysctl.h>
16 #include <linux/wait.h>
17 #include <linux/rwsem.h>
18
19 #ifdef CONFIG_PROC_SYSCTL
20
get_uts(struct ctl_table * table)21 static void *get_uts(struct ctl_table *table)
22 {
23 char *which = table->data;
24 struct uts_namespace *uts_ns;
25
26 uts_ns = current->nsproxy->uts_ns;
27 which = (which - (char *)&init_uts_ns) + (char *)uts_ns;
28
29 return which;
30 }
31
32 /*
33 * Special case of dostring for the UTS structure. This has locks
34 * to observe. Should this be in kernel/sys.c ????
35 */
proc_do_uts_string(struct ctl_table * table,int write,void __user * buffer,size_t * lenp,loff_t * ppos)36 static int proc_do_uts_string(struct ctl_table *table, int write,
37 void __user *buffer, size_t *lenp, loff_t *ppos)
38 {
39 struct ctl_table uts_table;
40 int r;
41 char tmp_data[__NEW_UTS_LEN + 1];
42
43 memcpy(&uts_table, table, sizeof(uts_table));
44 uts_table.data = tmp_data;
45
46 /*
47 * Buffer the value in tmp_data so that proc_dostring() can be called
48 * without holding any locks.
49 * We also need to read the original value in the write==1 case to
50 * support partial writes.
51 */
52 down_read(&uts_sem);
53 memcpy(tmp_data, get_uts(table), sizeof(tmp_data));
54 up_read(&uts_sem);
55 r = proc_dostring(&uts_table, write, buffer, lenp, ppos);
56
57 if (write) {
58 /*
59 * Write back the new value.
60 * Note that, since we dropped uts_sem, the result can
61 * theoretically be incorrect if there are two parallel writes
62 * at non-zero offsets to the same sysctl.
63 */
64 down_write(&uts_sem);
65 memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
66 up_write(&uts_sem);
67 proc_sys_poll_notify(table->poll);
68 }
69
70 return r;
71 }
72 #else
73 #define proc_do_uts_string NULL
74 #endif
75
76 static DEFINE_CTL_TABLE_POLL(hostname_poll);
77 static DEFINE_CTL_TABLE_POLL(domainname_poll);
78
79 static struct ctl_table uts_kern_table[] = {
80 {
81 .procname = "ostype",
82 .data = init_uts_ns.name.sysname,
83 .maxlen = sizeof(init_uts_ns.name.sysname),
84 .mode = 0444,
85 .proc_handler = proc_do_uts_string,
86 },
87 {
88 .procname = "osrelease",
89 .data = init_uts_ns.name.release,
90 .maxlen = sizeof(init_uts_ns.name.release),
91 .mode = 0444,
92 .proc_handler = proc_do_uts_string,
93 },
94 {
95 .procname = "version",
96 .data = init_uts_ns.name.version,
97 .maxlen = sizeof(init_uts_ns.name.version),
98 .mode = 0444,
99 .proc_handler = proc_do_uts_string,
100 },
101 {
102 .procname = "hostname",
103 .data = init_uts_ns.name.nodename,
104 .maxlen = sizeof(init_uts_ns.name.nodename),
105 .mode = 0644,
106 .proc_handler = proc_do_uts_string,
107 .poll = &hostname_poll,
108 },
109 {
110 .procname = "domainname",
111 .data = init_uts_ns.name.domainname,
112 .maxlen = sizeof(init_uts_ns.name.domainname),
113 .mode = 0644,
114 .proc_handler = proc_do_uts_string,
115 .poll = &domainname_poll,
116 },
117 {}
118 };
119
120 static struct ctl_table uts_root_table[] = {
121 {
122 .procname = "kernel",
123 .mode = 0555,
124 .child = uts_kern_table,
125 },
126 {}
127 };
128
129 #ifdef CONFIG_PROC_SYSCTL
130 /*
131 * Notify userspace about a change in a certain entry of uts_kern_table,
132 * identified by the parameter proc.
133 */
uts_proc_notify(enum uts_proc proc)134 void uts_proc_notify(enum uts_proc proc)
135 {
136 struct ctl_table *table = &uts_kern_table[proc];
137
138 proc_sys_poll_notify(table->poll);
139 }
140 #endif
141
utsname_sysctl_init(void)142 static int __init utsname_sysctl_init(void)
143 {
144 register_sysctl_table(uts_root_table);
145 return 0;
146 }
147
148 device_initcall(utsname_sysctl_init);
149
