[src/trunk]: src/sys/kern Add additional hardening in PT_TRACE_ME and PT_ATTACH

[kamil <kamil%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/8b9258640d7a
branches:  trunk
changeset: 361493:8b9258640d7a
user:      kamil <kamil%NetBSD.org@localhost>
date:      Tue May 01 14:09:53 2018 +0000

description:
Add additional hardening in PT_TRACE_ME and PT_ATTACH

Prohibit:
 - calling PT_TRACE_ME by initproc (PID1),
 - calling PT_ATTACH by initproc (PID1).

PID1 and its parent cannot become a tracer.

Sponsored by <The NetBSD Foundation>

diffstat:

 sys/kern/sys_ptrace_common.c |  24 ++++++++++++++++++------
 1 files changed, 18 insertions(+), 6 deletions(-)

diffs (62 lines):

diff -r 70585e319f83 -r 8b9258640d7a sys/kern/sys_ptrace_common.c
--- a/sys/kern/sys_ptrace_common.c      Tue May 01 13:48:38 2018 +0000
+++ b/sys/kern/sys_ptrace_common.c      Tue May 01 14:09:53 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_ptrace_common.c,v 1.38 2018/04/29 04:28:09 kamil Exp $     */
+/*     $NetBSD: sys_ptrace_common.c,v 1.39 2018/05/01 14:09:53 kamil Exp $     */
 
 /*-
  * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
@@ -118,7 +118,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_ptrace_common.c,v 1.38 2018/04/29 04:28:09 kamil Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_ptrace_common.c,v 1.39 2018/05/01 14:09:53 kamil Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ptrace.h"
@@ -385,7 +385,13 @@
                        return EPERM;
 
                /*
-                *      (2) the child is already traced.
+                *      (2) the process is initproc, or
+                */
+               if (p == initproc)
+                       return EPERM;
+
+               /*
+                *      (3) the child is already traced.
                 */
                if (ISSET(p->p_slflag, PSL_TRACED))
                        return EBUSY;
@@ -401,19 +407,25 @@
                        return EINVAL;
 
                /*
-                *      (2) it's a system process
+                *      (2) it's a system process,
                 */
                if (t->p_flag & PK_SYSTEM)
                        return EPERM;
 
                /*
-                *      (3) it's already being traced, or
+                *      (3) the tracer is initproc,
+                */
+               if (p == initproc)
+                       return EPERM;
+
+               /*
+                *      (4) it's already being traced, or
                 */
                if (ISSET(t->p_slflag, PSL_TRACED))
                        return EBUSY;
 
                /*
-                *      (4) the tracer is chrooted, and its root directory is
+                *      (5) the tracer is chrooted, and its root directory is
                 *          not at or above the root directory of the tracee
                 */
                mutex_exit(t->p_lock);  /* XXXSMP */