bf3c575ea1
cap_funwrap() and cap_funwrap_mmap() unwrap capabilities, exposing the underlying object. Attempting to unwrap a capability with an inadequate rights mask (e.g. calling cap_funwrap(fp, CAP_WRITE | CAP_MMAP, &result) on a capability whose rights mask is CAP_READ | CAP_MMAP) will result in ENOTCAPABLE. Unwrapping a non-capability is effectively a no-op. These functions will be used by Capsicum-aware versions of _fget(), etc. Approved by: mentor (rwatson), re (Capsicum blanket) Sponsored by: Google Inc
241 lines
6.1 KiB
C
241 lines
6.1 KiB
C
/*-
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* Copyright (c) 2008-2011 Robert N. M. Watson
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* Copyright (c) 2010-2011 Jonathan Anderson
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* All rights reserved.
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*
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* This software was developed at the University of Cambridge Computer
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* Laboratory with support from a grant from Google, Inc.
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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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/*
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* FreeBSD kernel capability facility.
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*
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* Currently, this file implements only capability mode; capabilities
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* (rights-refined file descriptors) will follow.
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*
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*/
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#include "opt_capsicum.h"
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/capability.h>
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#include <sys/file.h>
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#include <sys/filedesc.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/sysproto.h>
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#include <sys/sysctl.h>
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#include <sys/systm.h>
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#include <sys/ucred.h>
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#include <security/audit/audit.h>
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#include <vm/uma.h>
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#include <vm/vm.h>
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#ifdef CAPABILITY_MODE
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FEATURE(security_capabilities, "Capsicum Capability Mode");
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/*
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* System call to enter capability mode for the process.
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*/
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int
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cap_enter(struct thread *td, struct cap_enter_args *uap)
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{
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struct ucred *newcred, *oldcred;
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struct proc *p;
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if (IN_CAPABILITY_MODE(td))
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return (0);
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newcred = crget();
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p = td->td_proc;
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PROC_LOCK(p);
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oldcred = p->p_ucred;
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crcopy(newcred, oldcred);
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newcred->cr_flags |= CRED_FLAG_CAPMODE;
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p->p_ucred = newcred;
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PROC_UNLOCK(p);
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crfree(oldcred);
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return (0);
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}
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/*
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* System call to query whether the process is in capability mode.
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*/
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int
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cap_getmode(struct thread *td, struct cap_getmode_args *uap)
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{
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u_int i;
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i = (IN_CAPABILITY_MODE(td)) ? 1 : 0;
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return (copyout(&i, uap->modep, sizeof(i)));
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}
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#else /* !CAPABILITY_MODE */
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int
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cap_enter(struct thread *td, struct cap_enter_args *uap)
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{
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return (ENOSYS);
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}
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int
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cap_getmode(struct thread *td, struct cap_getmode_args *uap)
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{
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return (ENOSYS);
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}
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#endif /* CAPABILITY_MODE */
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#ifdef CAPABILITIES
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/*
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* struct capability describes a capability, and is hung off of its struct
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* file f_data field. cap_file and cap_rightss are static once hooked up, as
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* neither the object it references nor the rights it encapsulates are
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* permitted to change. cap_filelist may change when other capabilites are
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* added or removed from the same file, and is currently protected by the
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* pool mutex for the object file descriptor.
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*/
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struct capability {
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struct file *cap_object; /* Underlying object's file. */
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struct file *cap_file; /* Back-pointer to cap's file. */
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cap_rights_t cap_rights; /* Mask of rights on object. */
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LIST_ENTRY(capability) cap_filelist; /* Object's cap list. */
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};
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/*
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* Test whether a capability grants the requested rights.
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*/
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static int
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cap_check(struct capability *c, cap_rights_t rights)
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{
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if ((c->cap_rights | rights) != c->cap_rights)
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return (ENOTCAPABLE);
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return (0);
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}
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/*
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* Given a file descriptor, test it against a capability rights mask and then
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* return the file descriptor on which to actually perform the requested
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* operation. As long as the reference to fp_cap remains valid, the returned
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* pointer in *fp will remain valid, so no extra reference management is
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* required, and the caller should fdrop() fp_cap as normal when done with
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* both.
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*/
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int
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cap_funwrap(struct file *fp_cap, cap_rights_t rights, struct file **fpp)
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{
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struct capability *c;
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int error;
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if (fp_cap->f_type != DTYPE_CAPABILITY) {
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*fpp = fp_cap;
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return (0);
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}
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c = fp_cap->f_data;
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error = cap_check(c, rights);
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if (error)
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return (error);
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*fpp = c->cap_object;
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return (0);
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}
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/*
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* Slightly different routine for memory mapping file descriptors: unwrap the
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* capability and check CAP_MMAP, but also return a bitmask representing the
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* maximum mapping rights the capability allows on the object.
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*/
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int
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cap_funwrap_mmap(struct file *fp_cap, cap_rights_t rights, u_char *maxprotp,
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struct file **fpp)
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{
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struct capability *c;
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u_char maxprot;
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int error;
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if (fp_cap->f_type != DTYPE_CAPABILITY) {
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*fpp = fp_cap;
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*maxprotp = VM_PROT_ALL;
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return (0);
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}
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c = fp_cap->f_data;
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error = cap_check(c, rights | CAP_MMAP);
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if (error)
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return (error);
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*fpp = c->cap_object;
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maxprot = 0;
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if (c->cap_rights & CAP_READ)
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maxprot |= VM_PROT_READ;
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if (c->cap_rights & CAP_WRITE)
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maxprot |= VM_PROT_WRITE;
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if (c->cap_rights & CAP_MAPEXEC)
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maxprot |= VM_PROT_EXECUTE;
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*maxprotp = maxprot;
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return (0);
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}
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#else /* !CAPABILITIES */
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/*
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* Stub Capability functions for when options CAPABILITIES isn't compiled
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* into the kernel.
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*/
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int
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cap_funwrap(struct file *fp_cap, cap_rights_t rights, struct file **fpp)
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{
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KASSERT(fp_cap->f_type != DTYPE_CAPABILITY,
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("cap_funwrap: saw capability"));
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*fpp = fp_cap;
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return (0);
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}
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int
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cap_funwrap_mmap(struct file *fp_cap, cap_rights_t rights, u_char *maxprotp,
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struct file **fpp)
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{
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KASSERT(fp_cap->f_type != DTYPE_CAPABILITY,
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("cap_funwrap_mmap: saw capability"));
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*fpp = fp_cap;
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*maxprotp = VM_PROT_ALL;
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return (0);
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}
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#endif /* CAPABILITIES */
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