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reject attempts to map an immutable or append-only file, shared with

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write protection.  this stops data corruption where it was possible
to change the in-memory copy of an append-only file (but not the on-disk
copy).  this is documented in NetBSD security advisory 1998-003.  thanks
to darrenr, lukem, cgd, mycroft and mrg for this.
This commit is contained in:
mrg 1998-05-10 12:35:58 +00:00
parent ff93d40dbb
commit 6b11eea5b2
2 changed files with 37 additions and 7 deletions
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23
sys/uvm/uvm_mmap.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: uvm_mmap.c,v 1.8 1998/04/01 21:43:52 tv Exp $ */
/* $NetBSD: uvm_mmap.c,v 1.9 1998/05/10 12:35:59 mrg Exp $ */
/*
* XXXCDC: "ROUGH DRAFT" QUALITY UVM PRE-RELEASE FILE!
@ -64,6 +64,7 @@
#include <sys/malloc.h>
#include <sys/vnode.h>
#include <sys/conf.h>
#include <sys/stat.h>
#include <miscfs/specfs/specdev.h>
@ -211,6 +212,7 @@ sys_mmap(p, v, retval)
syscallarg(off_t) pos;
} */ *uap = v;
vm_offset_t addr;
struct vattr va;
off_t pos;
vm_size_t size, pageoff;
vm_prot_t prot, maxprot;
@ -354,10 +356,23 @@ sys_mmap(p, v, retval)
else if (prot & PROT_READ)
return (EACCES);
/* check write case (if shared) */
/* check write access, shared case first */
if (flags & MAP_SHARED) {
if (fp->f_flag & FWRITE)
maxprot |= VM_PROT_WRITE;
/*
* if the file is writable, only add PROT_WRITE to
* maxprot if the file is not immutable, append-only.
* otherwise, if we have asked for PROT_WRITE, return
* EPERM.
*/
if (fp->f_flag & FWRITE) {
if ((error =
VOP_GETATTR(vp, &va, p->p_ucred, p)))
return (error);
if ((va.va_flags & (IMMUTABLE|APPEND)) == 0)
maxprot |= VM_PROT_WRITE;
else if (prot & PROT_WRITE)
return (EPERM);
}
else if (prot & PROT_WRITE)
return (EACCES);
} else {

21
sys/vm/vm_mmap.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: vm_mmap.c,v 1.56 1998/03/28 16:58:30 kleink Exp $ */
/* $NetBSD: vm_mmap.c,v 1.57 1998/05/10 12:35:58 mrg Exp $ */
/*
* Copyright (c) 1988 University of Utah.
@ -55,6 +55,7 @@
#include <sys/file.h>
#include <sys/mman.h>
#include <sys/conf.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <sys/syscallargs.h>
@ -130,6 +131,7 @@ sys_mmap(p, v, retval)
syscallarg(long) pad;
syscallarg(off_t) pos;
} */ *uap = v;
struct vattr va;
register struct filedesc *fdp = p->p_fd;
register struct file *fp;
struct vnode *vp;
@ -263,8 +265,21 @@ sys_mmap(p, v, retval)
else if (prot & PROT_READ)
return (EACCES);
if (flags & MAP_SHARED) {
if (fp->f_flag & FWRITE)
maxprot |= VM_PROT_WRITE;
/*
* if the file is writable, only add PROT_WRITE to
* maxprot if the file is not immutable, append-only.
* otherwise, if we have asked for PROT_WRITE, return
* EPERM.
*/
if (fp->f_flag & FWRITE) {
if ((error =
VOP_GETATTR(vp, &va, p->p_ucred, p)))
return (error);
if ((va.va_flags & (IMMUTABLE|APPEND)) == 0)
maxprot |= VM_PROT_WRITE;
else if (prot & PROT_WRITE)
return (EPERM);
}
else if (prot & PROT_WRITE)
return (EACCES);
} else