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/sysctl.h>
12 #include <linux/wait.h>
13 #include <linux/rwsem.h>
14
15 #ifdef CONFIG_PROC_SYSCTL
16
get_uts(struct ctl_table * table)17 static void *get_uts(struct ctl_table *table)
18 {
19 char *which = table->data;
20 struct uts_namespace *uts_ns;
21
22 uts_ns = current->nsproxy->uts_ns;
23 which = (which - (char *)&init_uts_ns) + (char *)uts_ns;
24
25 return which;
26 }
27
28 /*
29 * Special case of dostring for the UTS structure. This has locks
30 * to observe. Should this be in kernel/sys.c ????
31 */
proc_do_uts_string(struct ctl_table * table,int write,void __user * buffer,size_t * lenp,loff_t * ppos)32 static int proc_do_uts_string(struct ctl_table *table, int write,
33 void __user *buffer, size_t *lenp, loff_t *ppos)
34 {
35 struct ctl_table uts_table;
36 int r;
37 char tmp_data[__NEW_UTS_LEN + 1];
38
39 memcpy(&uts_table, table, sizeof(uts_table));
40 uts_table.data = tmp_data;
41
42 /*
43 * Buffer the value in tmp_data so that proc_dostring() can be called
44 * without holding any locks.
45 * We also need to read the original value in the write==1 case to
46 * support partial writes.
47 */
48 down_read(&uts_sem);
49 memcpy(tmp_data, get_uts(table), sizeof(tmp_data));
50 up_read(&uts_sem);
51 r = proc_dostring(&uts_table, write, buffer, lenp, ppos);
52
53 if (write) {
54 /*
55 * Write back the new value.
56 * Note that, since we dropped uts_sem, the result can
57 * theoretically be incorrect if there are two parallel writes
58 * at non-zero offsets to the same sysctl.
59 */
60 down_write(&uts_sem);
61 memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
62 up_write(&uts_sem);
63 proc_sys_poll_notify(table->poll);
64 }
65
66 return r;
67 }
68 #else
69 #define proc_do_uts_string NULL
70 #endif
71
72 static DEFINE_CTL_TABLE_POLL(hostname_poll);
73 static DEFINE_CTL_TABLE_POLL(domainname_poll);
74
75 static struct ctl_table uts_kern_table[] = {
76 {
77 .procname = "ostype",
78 .data = init_uts_ns.name.sysname,
79 .maxlen = sizeof(init_uts_ns.name.sysname),
80 .mode = 0444,
81 .proc_handler = proc_do_uts_string,
82 },
83 {
84 .procname = "osrelease",
85 .data = init_uts_ns.name.release,
86 .maxlen = sizeof(init_uts_ns.name.release),
87 .mode = 0444,
88 .proc_handler = proc_do_uts_string,
89 },
90 {
91 .procname = "version",
92 .data = init_uts_ns.name.version,
93 .maxlen = sizeof(init_uts_ns.name.version),
94 .mode = 0444,
95 .proc_handler = proc_do_uts_string,
96 },
97 {
98 .procname = "hostname",
99 .data = init_uts_ns.name.nodename,
100 .maxlen = sizeof(init_uts_ns.name.nodename),
101 .mode = 0644,
102 .proc_handler = proc_do_uts_string,
103 .poll = &hostname_poll,
104 },
105 {
106 .procname = "domainname",
107 .data = init_uts_ns.name.domainname,
108 .maxlen = sizeof(init_uts_ns.name.domainname),
109 .mode = 0644,
110 .proc_handler = proc_do_uts_string,
111 .poll = &domainname_poll,
112 },
113 {}
114 };
115
116 static struct ctl_table uts_root_table[] = {
117 {
118 .procname = "kernel",
119 .mode = 0555,
120 .child = uts_kern_table,
121 },
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 */
uts_proc_notify(enum uts_proc proc)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
utsname_sysctl_init(void)138 static int __init utsname_sysctl_init(void)
139 {
140 register_sysctl_table(uts_root_table);
141 return 0;
142 }
143
144 device_initcall(utsname_sysctl_init);
145