8e38aeff17
implement shm_open(2) and shm_unlink(2) in the kernel: - Each shared memory file descriptor is associated with a swap-backed vm object which provides the backing store. Each descriptor starts off with a size of zero, but the size can be altered via ftruncate(2). The shared memory file descriptors also support fstat(2). read(2), write(2), ioctl(2), select(2), poll(2), and kevent(2) are not supported on shared memory file descriptors. - shm_open(2) and shm_unlink(2) are now implemented as system calls that manage shared memory file descriptors. The virtual namespace that maps pathnames to shared memory file descriptors is implemented as a hash table where the hash key is generated via the 32-bit Fowler/Noll/Vo hash of the pathname. - As an extension, the constant 'SHM_ANON' may be specified in place of the path argument to shm_open(2). In this case, an unnamed shared memory file descriptor will be created similar to the IPC_PRIVATE key for shmget(2). Note that the shared memory object can still be shared among processes by sharing the file descriptor via fork(2) or sendmsg(2), but it is unnamed. This effectively serves to implement the getmemfd() idea bandied about the lists several times over the years. - The backing store for shared memory file descriptors are garbage collected when they are not referenced by any open file descriptors or the shm_open(2) virtual namespace. Submitted by: dillon, peter (previous versions) Submitted by: rwatson (I based this on his version) Reviewed by: alc (suggested converting getmemfd() to shm_open())
147 lines
3.7 KiB
C
147 lines
3.7 KiB
C
/*-
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* Copyright (c) 2003-2006 SPARTA, Inc.
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* All rights reserved.
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*
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* This software was developed for the FreeBSD Project in part by Network
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* Associates Laboratories, the Security Research Division of Network
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* Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
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* as part of the DARPA CHATS research program.
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*
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* This software was enhanced by SPARTA ISSO under SPAWAR contract
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* N66001-04-C-6019 ("SEFOS").
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_mac.h"
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#include <sys/param.h>
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#include <sys/kernel.h>
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#include <sys/mman.h>
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#include <sys/malloc.h>
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#include <sys/module.h>
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#include <sys/systm.h>
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#include <sys/sysctl.h>
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#include <security/mac/mac_framework.h>
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#include <security/mac/mac_internal.h>
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#include <security/mac/mac_policy.h>
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static struct label *
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mac_posixshm_label_alloc(void)
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{
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struct label *label;
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label = mac_labelzone_alloc(M_WAITOK);
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MAC_PERFORM(posixshm_init_label, label);
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return (label);
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}
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void
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mac_posixshm_init(struct shmfd *shmfd)
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{
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shmfd->shm_label = mac_posixshm_label_alloc();
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}
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static void
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mac_posixshm_label_free(struct label *label)
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{
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MAC_PERFORM(posixshm_destroy_label, label);
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mac_labelzone_free(label);
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}
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void
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mac_posixshm_destroy(struct shmfd *shmfd)
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{
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mac_posixshm_label_free(shmfd->shm_label);
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shmfd->shm_label = NULL;
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}
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void
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mac_posixshm_create(struct ucred *cred, struct shmfd *shmfd)
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{
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MAC_PERFORM(posixshm_create, cred, shmfd, shmfd->shm_label);
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}
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int
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mac_posixshm_check_mmap(struct ucred *cred, struct shmfd *shmfd, int prot,
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int flags)
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{
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int error;
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MAC_CHECK(posixshm_check_mmap, cred, shmfd, shmfd->shm_label, prot,
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flags);
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return (error);
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}
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int
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mac_posixshm_check_open(struct ucred *cred, struct shmfd *shmfd)
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{
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int error;
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MAC_CHECK(posixshm_check_open, cred, shmfd, shmfd->shm_label);
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return (error);
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}
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int
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mac_posixshm_check_stat(struct ucred *active_cred, struct ucred *file_cred,
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struct shmfd *shmfd)
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{
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int error;
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MAC_CHECK(posixshm_check_stat, active_cred, file_cred, shmfd,
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shmfd->shm_label);
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return (error);
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}
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int
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mac_posixshm_check_truncate(struct ucred *active_cred, struct ucred *file_cred,
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struct shmfd *shmfd)
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{
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int error;
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MAC_CHECK(posixshm_check_truncate, active_cred, file_cred, shmfd,
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shmfd->shm_label);
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return (error);
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}
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int
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mac_posixshm_check_unlink(struct ucred *cred, struct shmfd *shmfd)
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{
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int error;
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MAC_CHECK(posixshm_check_unlink, cred, shmfd, shmfd->shm_label);
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return (error);
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}
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