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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Mon, 3 Jun 2013 04:32:54 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r251285 - head/sys/kern
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Author: kib
Date: Mon Jun  3 04:32:53 2013
New Revision: 251285
URL: http://svnweb.freebsd.org/changeset/base/251285

Log:
  Do not map the shared page COW.  If the process wired its address
  space, fork(2) would cause shadowing of the physical object and
  copying of the shared page into private copy, effectively preventing
  updates for the exported timehands structure and stopping the clock.
  
  Specify the maximum allowed permissions for the page to be read and
  execute, preventing write from the user mode.
  
  Reported and tested by:	<huanghwh@yahoo.com>
  Sponsored by:	The FreeBSD Foundation
  MFC after:	2 weeks

Modified:
  head/sys/kern/kern_exec.c

Modified: head/sys/kern/kern_exec.c
==============================================================================
--- head/sys/kern/kern_exec.c	Mon Jun  3 04:22:42 2013	(r251284)
+++ head/sys/kern/kern_exec.c	Mon Jun  3 04:32:53 2013	(r251285)
@@ -1050,8 +1050,9 @@ exec_new_vmspace(imgp, sv)
 		vm_object_reference(obj);
 		error = vm_map_fixed(map, obj, 0,
 		    sv->sv_shared_page_base, sv->sv_shared_page_len,
-		    VM_PROT_READ | VM_PROT_EXECUTE, VM_PROT_ALL,
-		    MAP_COPY_ON_WRITE | MAP_ACC_NO_CHARGE);
+		    VM_PROT_READ | VM_PROT_EXECUTE,
+		    VM_PROT_READ | VM_PROT_EXECUTE,
+		    MAP_INHERIT_SHARE | MAP_ACC_NO_CHARGE);
 		if (error) {
 			vm_object_deallocate(obj);
 			return (error);