kern_loginclass.c

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/*-
 * Copyright (c) 2011 The FreeBSD Foundation
 * All rights reserved.
 *
 * This software was developed by Edward Tomasz Napierala under sponsorship
 * from the FreeBSD Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $BSDSUniX$
 */

/*
 * Processes may set login class name using setloginclass(2).  This
 * is usually done through call to setusercontext(3), by programs
 * such as login(1), based on information from master.passwd(5).  Kernel
 * uses this information to enforce per-class resource limits.  Current
 * login class can be determined using id(1).  Login class is inherited
 * from the parent process during fork(2).  If not set, it defaults
 * to "default".
 *
 * Code in this file implements setloginclass(2) and getloginclass(2)
 * system calls, and maintains class name storage and retrieval.
 */

#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include <sys/param.h>
#include <sys/eventhandler.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/loginclass.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/types.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/queue.h>
#include <sys/racct.h>
#include <sys/refcount.h>
#include <sys/sysproto.h>
#include <sys/systm.h>

static MALLOC_DEFINE(M_LOGINCLASS, "loginclass", "loginclass structures");

LIST_HEAD(, loginclass) loginclasses;

/*
 * Lock protecting loginclasses list.
 */
static struct mtx loginclasses_lock;

static void lc_init(void);
SYSINIT(loginclass, SI_SUB_CPU, SI_ORDER_FIRST, lc_init, NULL);

void
loginclass_hold(struct loginclass *lc)
{

        refcount_acquire(&lc->lc_refcount);
}

void
loginclass_free(struct loginclass *lc)
{
        int old;

        old = lc->lc_refcount;
        if (old > 1 && atomic_cmpset_int(&lc->lc_refcount, old, old - 1))
                return;

        mtx_lock(&loginclasses_lock);
        if (refcount_release(&lc->lc_refcount)) {
                racct_destroy(&lc->lc_racct);
                LIST_REMOVE(lc, lc_next);
                mtx_unlock(&loginclasses_lock);
                free(lc, M_LOGINCLASS);

                return;
        }
        mtx_unlock(&loginclasses_lock);
}

/*
 * Return loginclass structure with a corresponding name.  Not
 * performance critical, as it's used mainly by setloginclass(2),
 * which happens once per login session.  Caller has to use
 * loginclass_free() on the returned value when it's no longer
 * needed.
 */
struct loginclass *
loginclass_find(const char *name)
{
        struct loginclass *lc, *newlc;

        if (name[0] == '\0' || strlen(name) >= MAXLOGNAME)
                return (NULL);

        newlc = malloc(sizeof(*newlc), M_LOGINCLASS, M_ZERO | M_WAITOK);
        racct_create(&newlc->lc_racct);

        mtx_lock(&loginclasses_lock);
        LIST_FOREACH(lc, &loginclasses, lc_next) {
                if (strcmp(name, lc->lc_name) != 0)
                        continue;

                /* Found loginclass with a matching name? */
                loginclass_hold(lc);
                mtx_unlock(&loginclasses_lock);
                racct_destroy(&newlc->lc_racct);
                free(newlc, M_LOGINCLASS);
                return (lc);
        }

        /* Add new loginclass. */
        strcpy(newlc->lc_name, name);
        refcount_init(&newlc->lc_refcount, 1);
        LIST_INSERT_HEAD(&loginclasses, newlc, lc_next);
        mtx_unlock(&loginclasses_lock);

        return (newlc);
}

/*
 * Get login class name.
 */
#ifndef _SYS_SYSPROTO_H_
struct getloginclass_args {
        char    *namebuf;
        size_t  namelen;
};
#endif
/* ARGSUSED */
int
sys_getloginclass(struct thread *td, struct getloginclass_args *uap)
{
        int error = 0;
        size_t lcnamelen;
        struct proc *p;
        struct loginclass *lc;

        p = td->td_proc;
        PROC_LOCK(p);
        lc = p->p_ucred->cr_loginclass;
        loginclass_hold(lc);
        PROC_UNLOCK(p);

        lcnamelen = strlen(lc->lc_name) + 1;
        if (lcnamelen > uap->namelen)
                error = ERANGE;
        if (error == 0)
                error = copyout(lc->lc_name, uap->namebuf, lcnamelen);
        loginclass_free(lc);
        return (error);
}

/*
 * Set login class name.
 */
#ifndef _SYS_SYSPROTO_H_
struct setloginclass_args {
        const char      *namebuf;
};
#endif
/* ARGSUSED */
int
sys_setloginclass(struct thread *td, struct setloginclass_args *uap)
{
        struct proc *p = td->td_proc;
        int error;
        char lcname[MAXLOGNAME];
        struct loginclass *newlc;
        struct ucred *newcred, *oldcred;

        error = priv_check(td, PRIV_PROC_SETLOGINCLASS);
        if (error != 0)
                return (error);
        error = copyinstr(uap->namebuf, lcname, sizeof(lcname), NULL);
        if (error != 0)
                return (error);

        newlc = loginclass_find(lcname);
        if (newlc == NULL)
                return (EINVAL);
        newcred = crget();

        PROC_LOCK(p);
        oldcred = crcopysafe(p, newcred);
        newcred->cr_loginclass = newlc;
        p->p_ucred = newcred;
        PROC_UNLOCK(p);
#ifdef RACCT
        racct_proc_ucred_changed(p, oldcred, newcred);
#endif
        loginclass_free(oldcred->cr_loginclass);
        crfree(oldcred);

        return (0);
}

void
loginclass_racct_foreach(void (*callback)(struct racct *racct,
    void *arg2, void *arg3), void *arg2, void *arg3)
{
        struct loginclass *lc;

        mtx_lock(&loginclasses_lock);
        LIST_FOREACH(lc, &loginclasses, lc_next)
                (callback)(lc->lc_racct, arg2, arg3);
        mtx_unlock(&loginclasses_lock);
}

static void
lc_init(void)
{

        mtx_init(&loginclasses_lock, "loginclasses lock", NULL, MTX_DEF);
}