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 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 */ 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 */ 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_table(uts_root_table); 141 return 0; 142 } 143 144 device_initcall(utsname_sysctl_init); 145