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