ipc_sysctl.c

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/*
 *  Copyright (C) 2007
 *
 *  Author: Eric Biederman <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License as
 *  published by the Free Software Foundation, version 2 of the
 *  License.
 */

#include <linux/module.h>
#include <linux/ipc.h>
#include <linux/nsproxy.h>
#include <linux/sysctl.h>
#include <linux/uaccess.h>
#include <linux/ipc_namespace.h>
#include <linux/msg.h>
#include "util.h"

static void *get_ipc(ctl_table *table)
{
    char *which = table->data;
    struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
    which = (which - (char *)&init_ipc_ns) + (char *)ipc_ns;
    return which;
}

#ifdef CONFIG_PROC_SYSCTL
static int proc_ipc_dointvec(ctl_table *table, int write,
    void __user *buffer, size_t *lenp, loff_t *ppos)
{
    struct ctl_table ipc_table;

    memcpy(&ipc_table, table, sizeof(ipc_table));
    ipc_table.data = get_ipc(table);

    return proc_dointvec(&ipc_table, write, buffer, lenp, ppos);
}

static int proc_ipc_dointvec_minmax(ctl_table *table, int write,
    void __user *buffer, size_t *lenp, loff_t *ppos)
{
    struct ctl_table ipc_table;

    memcpy(&ipc_table, table, sizeof(ipc_table));
    ipc_table.data = get_ipc(table);

    return proc_dointvec_minmax(&ipc_table, write, buffer, lenp, ppos);
}

static int proc_ipc_dointvec_minmax_orphans(ctl_table *table, int write,
    void __user *buffer, size_t *lenp, loff_t *ppos)
{
    struct ipc_namespace *ns = current->nsproxy->ipc_ns;
    int err = proc_ipc_dointvec_minmax(table, write, buffer, lenp, ppos);

    if (err < 0)
        return err;
    if (ns->shm_rmid_forced)
        shm_destroy_orphaned(ns);
    return err;
}

static int proc_ipc_callback_dointvec(ctl_table *table, int write,
    void __user *buffer, size_t *lenp, loff_t *ppos)
{
    struct ctl_table ipc_table;
    size_t lenp_bef = *lenp;
    int rc;

    memcpy(&ipc_table, table, sizeof(ipc_table));
    ipc_table.data = get_ipc(table);

    rc = proc_dointvec(&ipc_table, write, buffer, lenp, ppos);

    if (write && !rc && lenp_bef == *lenp)
        /*
         * Tunable has successfully been changed by hand. Disable its
         * automatic adjustment. This simply requires unregistering
         * the notifiers that trigger recalculation.
         */
        unregister_ipcns_notifier(current->nsproxy->ipc_ns);

    return rc;
}

static int proc_ipc_doulongvec_minmax(ctl_table *table, int write,
    void __user *buffer, size_t *lenp, loff_t *ppos)
{
    struct ctl_table ipc_table;
    memcpy(&ipc_table, table, sizeof(ipc_table));
    ipc_table.data = get_ipc(table);

    return proc_doulongvec_minmax(&ipc_table, write, buffer,
                    lenp, ppos);
}

/*
 * Routine that is called when the file "auto_msgmni" has successfully been
 * written.
 * Two values are allowed:
 * 0: unregister msgmni's callback routine from the ipc namespace notifier
 *    chain. This means that msgmni won't be recomputed anymore upon memory
 *    add/remove or ipc namespace creation/removal.
 * 1: register back the callback routine.
 */
static void ipc_auto_callback(int val)
{
    if (!val)
        unregister_ipcns_notifier(current->nsproxy->ipc_ns);
    else {
        /*
         * Re-enable automatic recomputing only if not already
         * enabled.
         */
        recompute_msgmni(current->nsproxy->ipc_ns);
        cond_register_ipcns_notifier(current->nsproxy->ipc_ns);
    }
}

static int proc_ipcauto_dointvec_minmax(ctl_table *table, int write,
    void __user *buffer, size_t *lenp, loff_t *ppos)
{
    struct ctl_table ipc_table;
    size_t lenp_bef = *lenp;
    int oldval;
    int rc;

    memcpy(&ipc_table, table, sizeof(ipc_table));
    ipc_table.data = get_ipc(table);
    oldval = *((int *)(ipc_table.data));

    rc = proc_dointvec_minmax(&ipc_table, write, buffer, lenp, ppos);

    if (write && !rc && lenp_bef == *lenp) {
        int newval = *((int *)(ipc_table.data));
        /*
         * The file "auto_msgmni" has correctly been set.
         * React by (un)registering the corresponding tunable, if the
         * value has changed.
         */
        if (newval != oldval)
            ipc_auto_callback(newval);
    }

    return rc;
}

#else
#define proc_ipc_doulongvec_minmax NULL
#define proc_ipc_dointvec      NULL
#define proc_ipc_dointvec_minmax   NULL
#define proc_ipc_dointvec_minmax_orphans   NULL
#define proc_ipc_callback_dointvec NULL
#define proc_ipcauto_dointvec_minmax NULL
#endif

static int zero;
static int one = 1;

static struct ctl_table ipc_kern_table[] = {
    {
        .procname   = "shmmax",
        .data       = &init_ipc_ns.shm_ctlmax,
        .maxlen     = sizeof (init_ipc_ns.shm_ctlmax),
        .mode       = 0644,
        .proc_handler   = proc_ipc_doulongvec_minmax,
    },
    {
        .procname   = "shmall",
        .data       = &init_ipc_ns.shm_ctlall,
        .maxlen     = sizeof (init_ipc_ns.shm_ctlall),
        .mode       = 0644,
        .proc_handler   = proc_ipc_doulongvec_minmax,
    },
    {
        .procname   = "shmmni",
        .data       = &init_ipc_ns.shm_ctlmni,
        .maxlen     = sizeof (init_ipc_ns.shm_ctlmni),
        .mode       = 0644,
        .proc_handler   = proc_ipc_dointvec,
    },
    {
        .procname   = "shm_rmid_forced",
        .data       = &init_ipc_ns.shm_rmid_forced,
        .maxlen     = sizeof(init_ipc_ns.shm_rmid_forced),
        .mode       = 0644,
        .proc_handler   = proc_ipc_dointvec_minmax_orphans,
        .extra1     = &zero,
        .extra2     = &one,
    },
    {
        .procname   = "msgmax",
        .data       = &init_ipc_ns.msg_ctlmax,
        .maxlen     = sizeof (init_ipc_ns.msg_ctlmax),
        .mode       = 0644,
        .proc_handler   = proc_ipc_dointvec,
    },
    {
        .procname   = "msgmni",
        .data       = &init_ipc_ns.msg_ctlmni,
        .maxlen     = sizeof (init_ipc_ns.msg_ctlmni),
        .mode       = 0644,
        .proc_handler   = proc_ipc_callback_dointvec,
    },
    {
        .procname   =  "msgmnb",
        .data       = &init_ipc_ns.msg_ctlmnb,
        .maxlen     = sizeof (init_ipc_ns.msg_ctlmnb),
        .mode       = 0644,
        .proc_handler   = proc_ipc_dointvec,
    },
    {
        .procname   = "sem",
        .data       = &init_ipc_ns.sem_ctls,
        .maxlen     = 4*sizeof (int),
        .mode       = 0644,
        .proc_handler   = proc_ipc_dointvec,
    },
    {
        .procname   = "auto_msgmni",
        .data       = &init_ipc_ns.auto_msgmni,
        .maxlen     = sizeof(int),
        .mode       = 0644,
        .proc_handler   = proc_ipcauto_dointvec_minmax,
        .extra1     = &zero,
        .extra2     = &one,
    },
    {}
};

static struct ctl_table ipc_root_table[] = {
    {
        .procname   = "kernel",
        .mode       = 0555,
        .child      = ipc_kern_table,
    },
    {}
};

static int __init ipc_sysctl_init(void)
{
    register_sysctl_table(ipc_root_table);
    return 0;
}

__initcall(ipc_sysctl_init);