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Thomas Gleixnerb886d83c2019-06-01 10:08:55 +02001// SPDX-License-Identifier: GPL-2.0-only
Eric W. Biederman39732ac2007-02-14 00:33:58 -08002/*
3 * Copyright (C) 2007
4 *
5 * Author: Eric Biederman <ebiederm@xmision.com>
Eric W. Biederman39732ac2007-02-14 00:33:58 -08006 */
7
Paul Gortmaker9984de12011-05-23 14:51:41 -04008#include <linux/export.h>
Eric W. Biederman39732ac2007-02-14 00:33:58 -08009#include <linux/uts.h>
10#include <linux/utsname.h>
Jason A. Donenfeld37608ba2022-09-27 11:35:16 +020011#include <linux/random.h>
Eric W. Biederman39732ac2007-02-14 00:33:58 -080012#include <linux/sysctl.h>
Lucas De Marchif1ecf062011-11-02 13:39:22 -070013#include <linux/wait.h>
Ingo Molnarcd9c5132017-02-08 18:51:58 +010014#include <linux/rwsem.h>
Eric W. Biederman39732ac2007-02-14 00:33:58 -080015
Yuanhan Liucd89f462013-02-27 17:05:22 -080016#ifdef CONFIG_PROC_SYSCTL
17
Jann Horn42a0cc32018-06-25 18:34:10 +020018static void *get_uts(struct ctl_table *table)
Eric W. Biederman39732ac2007-02-14 00:33:58 -080019{
20 char *which = table->data;
Pavel Emelyanov32df81c2007-11-28 16:21:38 -080021 struct uts_namespace *uts_ns;
22
23 uts_ns = current->nsproxy->uts_ns;
24 which = (which - (char *)&init_uts_ns) + (char *)uts_ns;
Cedric Le Goater7d69a1f2007-07-15 23:40:58 -070025
Eric W. Biederman39732ac2007-02-14 00:33:58 -080026 return which;
27}
28
Eric W. Biederman39732ac2007-02-14 00:33:58 -080029/*
30 * Special case of dostring for the UTS structure. This has locks
31 * to observe. Should this be in kernel/sys.c ????
32 */
Joe Perches6f8fd1d2014-06-06 14:38:08 -070033static int proc_do_uts_string(struct ctl_table *table, int write,
Christoph Hellwig32927392020-04-24 08:43:38 +020034 void *buffer, size_t *lenp, loff_t *ppos)
Eric W. Biederman39732ac2007-02-14 00:33:58 -080035{
36 struct ctl_table uts_table;
37 int r;
Jann Horn42a0cc32018-06-25 18:34:10 +020038 char tmp_data[__NEW_UTS_LEN + 1];
Lucas De Marchif1ecf062011-11-02 13:39:22 -070039
Jann Horn42a0cc32018-06-25 18:34:10 +020040 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 */
Jason A. Donenfeld37608ba2022-09-27 11:35:16 +020061 add_device_randomness(tmp_data, sizeof(tmp_data));
Jann Horn42a0cc32018-06-25 18:34:10 +020062 down_write(&uts_sem);
63 memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
64 up_write(&uts_sem);
Lucas De Marchif1ecf062011-11-02 13:39:22 -070065 proc_sys_poll_notify(table->poll);
Jann Horn42a0cc32018-06-25 18:34:10 +020066 }
Lucas De Marchif1ecf062011-11-02 13:39:22 -070067
Eric W. Biederman39732ac2007-02-14 00:33:58 -080068 return r;
69}
70#else
71#define proc_do_uts_string NULL
72#endif
73
Lucas De Marchif1ecf062011-11-02 13:39:22 -070074static DEFINE_CTL_TABLE_POLL(hostname_poll);
75static DEFINE_CTL_TABLE_POLL(domainname_poll);
76
Linus Torvalds52826d32022-10-23 12:01:01 -070077// Note: update 'enum uts_proc' to match any changes to this table
Eric W. Biederman39732ac2007-02-14 00:33:58 -080078static struct ctl_table uts_kern_table[] = {
79 {
Petr Vorelbfca3dd2022-09-01 21:44:03 +020080 .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 {
Eric W. Biederman39732ac2007-02-14 00:33:58 -080087 .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,
Eric W. Biederman39732ac2007-02-14 00:33:58 -080092 },
93 {
Eric W. Biederman39732ac2007-02-14 00:33:58 -080094 .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,
Eric W. Biederman39732ac2007-02-14 00:33:58 -080099 },
100 {
Eric W. Biederman39732ac2007-02-14 00:33:58 -0800101 .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,
Eric W. Biederman39732ac2007-02-14 00:33:58 -0800106 },
107 {
Eric W. Biederman39732ac2007-02-14 00:33:58 -0800108 .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,
Lucas De Marchif1ecf062011-11-02 13:39:22 -0700113 .poll = &hostname_poll,
Eric W. Biederman39732ac2007-02-14 00:33:58 -0800114 },
115 {
Eric W. Biederman39732ac2007-02-14 00:33:58 -0800116 .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,
Lucas De Marchif1ecf062011-11-02 13:39:22 -0700121 .poll = &domainname_poll,
Eric W. Biederman39732ac2007-02-14 00:33:58 -0800122 },
123 {}
124};
125
126static struct ctl_table uts_root_table[] = {
127 {
Eric W. Biederman39732ac2007-02-14 00:33:58 -0800128 .procname = "kernel",
129 .mode = 0555,
130 .child = uts_kern_table,
131 },
132 {}
133};
134
Lucas De Marchif1ecf062011-11-02 13:39:22 -0700135#ifdef CONFIG_PROC_SYSCTL
136/*
137 * Notify userspace about a change in a certain entry of uts_kern_table,
138 * identified by the parameter proc.
139 */
140void uts_proc_notify(enum uts_proc proc)
141{
142 struct ctl_table *table = &uts_kern_table[proc];
143
144 proc_sys_poll_notify(table->poll);
145}
146#endif
147
Eric W. Biederman39732ac2007-02-14 00:33:58 -0800148static int __init utsname_sysctl_init(void)
149{
Eric W. Biederman0b4d4142007-02-14 00:34:09 -0800150 register_sysctl_table(uts_root_table);
Eric W. Biederman39732ac2007-02-14 00:33:58 -0800151 return 0;
152}
153
Fabian Frederick95583e42014-06-04 16:11:26 -0700154device_initcall(utsname_sysctl_init);