svn commit: r214610 - head/sys/powerpc/aim

[Nathan Whitehorn]

Author: nwhitehorn
Date: Sun Oct 31 23:04:15 2010
New Revision: 214610
URL: http://svn.freebsd.org/changeset/base/214610

Log:
  Add a security nit to recent copyin/out changes: map the user segment
  no-execute in case of exploitable kernel bugs.
  
  MFC after:	1 week

Modified:
  head/sys/powerpc/aim/copyinout.c

Modified: head/sys/powerpc/aim/copyinout.c
==============================================================================
--- head/sys/powerpc/aim/copyinout.c	Sun Oct 31 23:03:11 2010	(r214609)
+++ head/sys/powerpc/aim/copyinout.c	Sun Oct 31 23:04:15 2010	(r214610)
@@ -95,6 +95,9 @@ set_user_sr(pmap_t pm, const void *addr)
 		slbv = slb->slbv;
 	}
 
+	/* Mark segment no-execute */
+	slbv |= SLBV_N;
+
 	/* If we have already set this VSID, we can just return */
 	if (curthread->td_pcb->pcb_cpu.aim.usr_vsid == slbv) 
 		return;
@@ -117,6 +120,9 @@ set_user_sr(pmap_t pm, const void *addr)
 	if (curthread->td_pcb->pcb_cpu.aim.usr_vsid == vsid)
 		return;
 
+	/* Mark segment no-execute */
+	vsid |= SR_N;
+
 	__asm __volatile("isync");
 	curthread->td_pcb->pcb_cpu.aim.usr_vsid = vsid;
 	__asm __volatile("mtsr %0,%1; isync" :: "n"(USER_SR), "r"(vsid));