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(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(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 static struct ctl_table uts_kern_table[] = { 78 { 79 .procname = "arch", 80 .data = init_uts_ns.name.machine, 81 .maxlen = sizeof(init_uts_ns.name.machine), 82 .mode = 0444, 83 .proc_handler = proc_do_uts_string, 84 }, 85 { 86 .procname = "ostype", 87 .data = init_uts_ns.name.sysname, 88 .maxlen = sizeof(init_uts_ns.name.sysname), 89 .mode = 0444, 90 .proc_handler = proc_do_uts_string, 91 }, 92 { 93 .procname = "osrelease", 94 .data = init_uts_ns.name.release, 95 .maxlen = sizeof(init_uts_ns.name.release), 96 .mode = 0444, 97 .proc_handler = proc_do_uts_string, 98 }, 99 { 100 .procname = "version", 101 .data = init_uts_ns.name.version, 102 .maxlen = sizeof(init_uts_ns.name.version), 103 .mode = 0444, 104 .proc_handler = proc_do_uts_string, 105 }, 106 { 107 .procname = "hostname", 108 .data = init_uts_ns.name.nodename, 109 .maxlen = sizeof(init_uts_ns.name.nodename), 110 .mode = 0644, 111 .proc_handler = proc_do_uts_string, 112 .poll = &hostname_poll, 113 }, 114 { 115 .procname = "domainname", 116 .data = init_uts_ns.name.domainname, 117 .maxlen = sizeof(init_uts_ns.name.domainname), 118 .mode = 0644, 119 .proc_handler = proc_do_uts_string, 120 .poll = &domainname_poll, 121 }, 122 {} 123 }; 124 125 static struct ctl_table uts_root_table[] = { 126 { 127 .procname = "kernel", 128 .mode = 0555, 129 .child = uts_kern_table, 130 }, 131 {} 132 }; 133 134 #ifdef CONFIG_PROC_SYSCTL 135 /* 136 * Notify userspace about a change in a certain entry of uts_kern_table, 137 * identified by the parameter proc. 138 */ 139 void uts_proc_notify(enum uts_proc proc) 140 { 141 struct ctl_table *table = &uts_kern_table[proc]; 142 143 proc_sys_poll_notify(table->poll); 144 } 145 #endif 146 147 static int __init utsname_sysctl_init(void) 148 { 149 register_sysctl_table(uts_root_table); 150 return 0; 151 } 152 153 device_initcall(utsname_sysctl_init); 154