The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/sysv_ipc.c

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    1 /*      $NetBSD: sysv_ipc.c,v 1.7 1994/06/29 06:33:11 cgd Exp $ */
    2 /*-
    3  * Copyright (c) 1994 Herb Peyerl <hpeyerl@novatel.ca>
    4  * All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. All advertising materials mentioning features or use of this software
   15  *    must display the following acknowledgement:
   16  *      This product includes software developed by Herb Peyerl.
   17  * 4. The name of Herb Peyerl may not be used to endorse or promote products
   18  *    derived from this software without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   21  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   22  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   23  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   24  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   25  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   29  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD$");
   34 
   35 #include "opt_sysvipc.h"
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h>
   39 #include <sys/sem.h>
   40 #include <sys/shm.h>
   41 #include <sys/ipc.h>
   42 #include <sys/proc.h>
   43 #include <sys/ucred.h>
   44 
   45 void (*shmfork_hook)(struct proc *, struct proc *) = NULL;
   46 void (*shmexit_hook)(struct vmspace *) = NULL;
   47 
   48 /* called from kern_fork.c */
   49 void
   50 shmfork(p1, p2)
   51         struct proc *p1, *p2;
   52 {
   53 
   54         if (shmfork_hook != NULL)
   55                 shmfork_hook(p1, p2);
   56         return;
   57 }
   58 
   59 /* called from kern_exit.c */
   60 void
   61 shmexit(struct vmspace *vm)
   62 {
   63 
   64         if (shmexit_hook != NULL)
   65                 shmexit_hook(vm);
   66         return;
   67 }
   68 
   69 /*
   70  * Check for IPC permission.
   71  *
   72  * Note: The MAC Framework does not require any modifications to the
   73  * ipcperm() function, as access control checks are performed throughout the
   74  * implementation of each primitive.  Those entry point calls complement the
   75  * ipcperm() discertionary checks.
   76  */
   77 int
   78 ipcperm(td, perm, mode)
   79         struct thread *td;
   80         struct ipc_perm *perm;
   81         int mode;
   82 {
   83         struct ucred *cred = td->td_ucred;
   84         int error;
   85 
   86         if (cred->cr_uid != perm->cuid && cred->cr_uid != perm->uid) {
   87                 /*
   88                  * For a non-create/owner, we require privilege to
   89                  * modify the object protections.  Note: some other
   90                  * implementations permit IPC_M to be delegated to
   91                  * unprivileged non-creator/owner uids/gids.
   92                  */
   93                 if (mode & IPC_M) {
   94                         error = suser(td);
   95                         if (error)
   96                                 return (error);
   97                 }
   98                 /*
   99                  * Try to match against creator/owner group; if not, fall
  100                  * back on other.
  101                  */
  102                 mode >>= 3;
  103                 if (!groupmember(perm->gid, cred) &&
  104                     !groupmember(perm->cgid, cred))
  105                         mode >>= 3;
  106         } else {
  107                 /*
  108                  * Always permit the creator/owner to update the object
  109                  * protections regardless of whether the object mode
  110                  * permits it.
  111                  */
  112                 if (mode & IPC_M)
  113                         return (0);
  114         }
  115 
  116         if ((mode & perm->mode) != mode) {
  117                 if (suser(td) != 0)
  118                         return (EACCES);
  119         }
  120         return (0);
  121 }

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