1 /* 2 * Copyright (C) 2007 3 * 4 * Author: Eric Biederman <ebiederm@xmision.com> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License as 8 * published by the Free Software Foundation, version 2 of the 9 * License. 10 */ 11 12 #include <linux/export.h> 13 #include <linux/uts.h> 14 #include <linux/utsname.h> 15 #include <linux/sysctl.h> 16 #include <linux/wait.h> 17 #include <linux/rwsem.h> 18 19 #ifdef CONFIG_PROC_SYSCTL 20 21 static void *get_uts(struct ctl_table *table) 22 { 23 char *which = table->data; 24 struct uts_namespace *uts_ns; 25 26 uts_ns = current->nsproxy->uts_ns; 27 which = (which - (char *)&init_uts_ns) + (char *)uts_ns; 28 29 return which; 30 } 31 32 /* 33 * Special case of dostring for the UTS structure. This has locks 34 * to observe. Should this be in kernel/sys.c ???? 35 */ 36 static int proc_do_uts_string(struct ctl_table *table, int write, 37 void __user *buffer, size_t *lenp, loff_t *ppos) 38 { 39 struct ctl_table uts_table; 40 int r; 41 char tmp_data[__NEW_UTS_LEN + 1]; 42 43 memcpy(&uts_table, table, sizeof(uts_table)); 44 uts_table.data = tmp_data; 45 46 /* 47 * Buffer the value in tmp_data so that proc_dostring() can be called 48 * without holding any locks. 49 * We also need to read the original value in the write==1 case to 50 * support partial writes. 51 */ 52 down_read(&uts_sem); 53 memcpy(tmp_data, get_uts(table), sizeof(tmp_data)); 54 up_read(&uts_sem); 55 r = proc_dostring(&uts_table, write, buffer, lenp, ppos); 56 57 if (write) { 58 /* 59 * Write back the new value. 60 * Note that, since we dropped uts_sem, the result can 61 * theoretically be incorrect if there are two parallel writes 62 * at non-zero offsets to the same sysctl. 63 */ 64 down_write(&uts_sem); 65 memcpy(get_uts(table), tmp_data, sizeof(tmp_data)); 66 up_write(&uts_sem); 67 proc_sys_poll_notify(table->poll); 68 } 69 70 return r; 71 } 72 #else 73 #define proc_do_uts_string NULL 74 #endif 75 76 static DEFINE_CTL_TABLE_POLL(hostname_poll); 77 static DEFINE_CTL_TABLE_POLL(domainname_poll); 78 79 static struct ctl_table uts_kern_table[] = { 80 { 81 .procname = "ostype", 82 .data = init_uts_ns.name.sysname, 83 .maxlen = sizeof(init_uts_ns.name.sysname), 84 .mode = 0444, 85 .proc_handler = proc_do_uts_string, 86 }, 87 { 88 .procname = "osrelease", 89 .data = init_uts_ns.name.release, 90 .maxlen = sizeof(init_uts_ns.name.release), 91 .mode = 0444, 92 .proc_handler = proc_do_uts_string, 93 }, 94 { 95 .procname = "version", 96 .data = init_uts_ns.name.version, 97 .maxlen = sizeof(init_uts_ns.name.version), 98 .mode = 0444, 99 .proc_handler = proc_do_uts_string, 100 }, 101 { 102 .procname = "hostname", 103 .data = init_uts_ns.name.nodename, 104 .maxlen = sizeof(init_uts_ns.name.nodename), 105 .mode = 0644, 106 .proc_handler = proc_do_uts_string, 107 .poll = &hostname_poll, 108 }, 109 { 110 .procname = "domainname", 111 .data = init_uts_ns.name.domainname, 112 .maxlen = sizeof(init_uts_ns.name.domainname), 113 .mode = 0644, 114 .proc_handler = proc_do_uts_string, 115 .poll = &domainname_poll, 116 }, 117 {} 118 }; 119 120 static struct ctl_table uts_root_table[] = { 121 { 122 .procname = "kernel", 123 .mode = 0555, 124 .child = uts_kern_table, 125 }, 126 {} 127 }; 128 129 #ifdef CONFIG_PROC_SYSCTL 130 /* 131 * Notify userspace about a change in a certain entry of uts_kern_table, 132 * identified by the parameter proc. 133 */ 134 void uts_proc_notify(enum uts_proc proc) 135 { 136 struct ctl_table *table = &uts_kern_table[proc]; 137 138 proc_sys_poll_notify(table->poll); 139 } 140 #endif 141 142 static int __init utsname_sysctl_init(void) 143 { 144 register_sysctl_table(uts_root_table); 145 return 0; 146 } 147 148 device_initcall(utsname_sysctl_init); 149