1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2007
4 *
5 * Author: Eric Biederman <ebiederm@xmision.com>
6 */
7
8 #include <linux/export.h>
9 #include <linux/uts.h>
10 #include <linux/utsname.h>
11 #include <linux/random.h>
12 #include <linux/sysctl.h>
13 #include <linux/wait.h>
14 #include <linux/rwsem.h>
15
16 #ifdef CONFIG_PROC_SYSCTL
17
18 static void *get_uts(const struct ctl_table *table)
19 {
20 char *which = table->data;
21 struct uts_namespace *uts_ns;
22
23 uts_ns = current->nsproxy->uts_ns;
24 which = (which - (char *)&init_uts_ns) + (char *)uts_ns;
25
26 return which;
27 }
28
29 /*
30 * Special case of dostring for the UTS structure. This has locks
31 * to observe. Should this be in kernel/sys.c ????
32 */
33 static int proc_do_uts_string(const struct ctl_table *table, int write,
34 void *buffer, size_t *lenp, loff_t *ppos)
35 {
36 struct ctl_table uts_table;
37 int r;
38 char tmp_data[__NEW_UTS_LEN + 1];
39
40 memcpy(&uts_table, table, sizeof(uts_table));
41 uts_table.data = tmp_data;
42
43 /*
44 * Buffer the value in tmp_data so that proc_dostring() can be called
45 * without holding any locks.
46 * We also need to read the original value in the write==1 case to
47 * support partial writes.
48 */
49 down_read(&uts_sem);
50 memcpy(tmp_data, get_uts(table), sizeof(tmp_data));
51 up_read(&uts_sem);
52 r = proc_dostring(&uts_table, write, buffer, lenp, ppos);
53
54 if (write) {
55 /*
56 * Write back the new value.
57 * Note that, since we dropped uts_sem, the result can
58 * theoretically be incorrect if there are two parallel writes
59 * at non-zero offsets to the same sysctl.
60 */
61 add_device_randomness(tmp_data, sizeof(tmp_data));
62 down_write(&uts_sem);
63 memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
64 up_write(&uts_sem);
65 proc_sys_poll_notify(table->poll);
66 }
67
68 return r;
69 }
70 #else
71 #define proc_do_uts_string NULL
72 #endif
73
74 static DEFINE_CTL_TABLE_POLL(hostname_poll);
75 static DEFINE_CTL_TABLE_POLL(domainname_poll);
76
77 // Note: update 'enum uts_proc' to match any changes to this table
78 static struct ctl_table uts_kern_table[] = {
79 {
80 .procname = "arch",
81 .data = init_uts_ns.name.machine,
82 .maxlen = sizeof(init_uts_ns.name.machine),
83 .mode = 0444,
84 .proc_handler = proc_do_uts_string,
85 },
86 {
87 .procname = "ostype",
88 .data = init_uts_ns.name.sysname,
89 .maxlen = sizeof(init_uts_ns.name.sysname),
90 .mode = 0444,
91 .proc_handler = proc_do_uts_string,
92 },
93 {
94 .procname = "osrelease",
95 .data = init_uts_ns.name.release,
96 .maxlen = sizeof(init_uts_ns.name.release),
97 .mode = 0444,
98 .proc_handler = proc_do_uts_string,
99 },
100 {
101 .procname = "version",
102 .data = init_uts_ns.name.version,
103 .maxlen = sizeof(init_uts_ns.name.version),
104 .mode = 0444,
105 .proc_handler = proc_do_uts_string,
106 },
107 {
108 .procname = "hostname",
109 .data = init_uts_ns.name.nodename,
110 .maxlen = sizeof(init_uts_ns.name.nodename),
111 .mode = 0644,
112 .proc_handler = proc_do_uts_string,
113 .poll = &hostname_poll,
114 },
115 {
116 .procname = "domainname",
117 .data = init_uts_ns.name.domainname,
118 .maxlen = sizeof(init_uts_ns.name.domainname),
119 .mode = 0644,
120 .proc_handler = proc_do_uts_string,
121 .poll = &domainname_poll,
122 },
123 };
124
125 #ifdef CONFIG_PROC_SYSCTL
126 /*
127 * Notify userspace about a change in a certain entry of uts_kern_table,
128 * identified by the parameter proc.
129 */
130 void uts_proc_notify(enum uts_proc proc)
131 {
132 struct ctl_table *table = &uts_kern_table[proc];
133
134 proc_sys_poll_notify(table->poll);
135 }
136 #endif
137
138 static int __init utsname_sysctl_init(void)
139 {
140 register_sysctl("kernel", uts_kern_table);
141 return 0;
142 }
143
144 device_initcall(utsname_sysctl_init);
145
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