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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Wed, 1 Jul 2015 16:37:03 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r285011 - head/sys/amd64/amd64
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Author: kib
Date: Wed Jul  1 16:37:03 2015
New Revision: 285011
URL: https://svnweb.freebsd.org/changeset/base/285011

Log:
  Disallow a debugger on 64bit system to set fs/gs bases of the 32bit
  process beyond the end of the process address space.  Such setting is
  not dangerous to the kernel integrity, but it causes confusing
  application misbehaviour.
  
  Sponsored by:	The FreeBSD Foundation
  MFC after:	12 days

Modified:
  head/sys/amd64/amd64/ptrace_machdep.c

Modified: head/sys/amd64/amd64/ptrace_machdep.c
==============================================================================
--- head/sys/amd64/amd64/ptrace_machdep.c	Wed Jul  1 15:54:13 2015	(r285010)
+++ head/sys/amd64/amd64/ptrace_machdep.c	Wed Jul  1 16:37:03 2015	(r285011)
@@ -231,7 +231,7 @@ cpu_ptrace(struct thread *td, int req, v
 		error = copyin(addr, &rv, sizeof(rv));
 		if (error != 0)
 			break;
-		if (rv >= VM_MAXUSER_ADDRESS) {
+		if (rv >= td->td_proc->p_sysent->sv_maxuser) {
 			error = EINVAL;
 			break;
 		}