Quelle utsname_sysctl.c Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
/*
*  Copyright (C) 2007
*
*  Author: Eric Biederman <ebiederm@xmision.com>
*/

#include <linux/export.h>
#include <linux/uts.h>
#include <linux/utsname.h>
#include <linux/random.h>
#include <linux/sysctl.h>
#include <linux/wait.h>
#include <linux/rwsem.h>

#ifdef CONFIG_PROC_SYSCTL

static void *get_uts(const struct ctl_table *table)
{
char *which = table->data;
struct uts_namespace *uts_ns;

uts_ns = current->nsproxy->uts_ns;
which = (which - (char *)&init_uts_ns) + (char *)uts_ns;

return which;
}

/*
* Special case of dostring for the UTS structure. This has locks
* to observe. Should this be in kernel/sys.c ????
*/
static int proc_do_uts_string(const struct ctl_table *table, int write,
    void *buffer, size_t *lenp, loff_t *ppos)
{
struct ctl_table uts_table;
int r;
char tmp_data[__NEW_UTS_LEN + 1];

memcpy(&uts_table, table, sizeof(uts_table));
uts_table.data = tmp_data;

/*
* Buffer the value in tmp_data so that proc_dostring() can be called
* without holding any locks.
* We also need to read the original value in the write==1 case to
* support partial writes.
*/
down_read(&uts_sem);
memcpy(tmp_data, get_uts(table), sizeof(tmp_data));
up_read(&uts_sem);
r = proc_dostring(&uts_table, write, buffer, lenp, ppos);

if (write) {
  /*
* Write back the new value.
* Note that, since we dropped uts_sem, the result can
* theoretically be incorrect if there are two parallel writes
* at non-zero offsets to the same sysctl.
*/
  add_device_randomness(tmp_data, sizeof(tmp_data));
  down_write(&uts_sem);
  memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
  up_write(&uts_sem);
  proc_sys_poll_notify(table->poll);
}

return r;
}
#else
#define proc_do_uts_string NULL
#endif

static DEFINE_CTL_TABLE_POLL(hostname_poll);
static DEFINE_CTL_TABLE_POLL(domainname_poll);

// Note: update 'enum uts_proc' to match any changes to this table
static const struct ctl_table uts_kern_table[] = {
{
  .procname = "arch",
  .data  = init_uts_ns.name.machine,
  .maxlen  = sizeof(init_uts_ns.name.machine),
  .mode  = 0444,
  .proc_handler = proc_do_uts_string,
},
{
  .procname = "ostype",
  .data  = init_uts_ns.name.sysname,
  .maxlen  = sizeof(init_uts_ns.name.sysname),
  .mode  = 0444,
  .proc_handler = proc_do_uts_string,
},
{
  .procname = "osrelease",
  .data  = init_uts_ns.name.release,
  .maxlen  = sizeof(init_uts_ns.name.release),
  .mode  = 0444,
  .proc_handler = proc_do_uts_string,
},
{
  .procname = "version",
  .data  = init_uts_ns.name.version,
  .maxlen  = sizeof(init_uts_ns.name.version),
  .mode  = 0444,
  .proc_handler = proc_do_uts_string,
},
{
  .procname = "hostname",
  .data  = init_uts_ns.name.nodename,
  .maxlen  = sizeof(init_uts_ns.name.nodename),
  .mode  = 0644,
  .proc_handler = proc_do_uts_string,
  .poll  = &hostname_poll,
},
{
  .procname = "domainname",
  .data  = init_uts_ns.name.domainname,
  .maxlen  = sizeof(init_uts_ns.name.domainname),
  .mode  = 0644,
  .proc_handler = proc_do_uts_string,
  .poll  = &domainname_poll,
},
};

#ifdef CONFIG_PROC_SYSCTL
/*
* Notify userspace about a change in a certain entry of uts_kern_table,
* identified by the parameter proc.
*/
void uts_proc_notify(enum uts_proc proc)
{
const struct ctl_table *table = &uts_kern_table[proc];

proc_sys_poll_notify(table->poll);
}
#endif

static int __init utsname_sysctl_init(void)
{
register_sysctl("kernel", uts_kern_table);
return 0;
}

device_initcall(utsname_sysctl_init);

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