[src/trunk]: src/sys/kern Disallow resuming program with PC=0x0 in ptrace(2)

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

details:   https://anonhg.NetBSD.org/src/rev/e0e769f3dfbd
branches:  trunk
changeset: 450972:e0e769f3dfbd
user:      kamil <kamil%NetBSD.org@localhost>
date:      Wed May 01 17:02:40 2019 +0000

description:
Disallow resuming program with PC=0x0 in ptrace(2)

If the address parameter is 0, report error.
It's a popular mistake to set Program Counter to 0x0.
In certain kernels this is allowable parameter and causes
portability issue.

Disallow explicitly zeroed PC, instead of triggering
a harder to debug crash later.

diffstat:

 sys/kern/sys_ptrace_common.c |  19 +++++++++++++++++--
 1 files changed, 17 insertions(+), 2 deletions(-)

diffs (40 lines):

diff -r c47e4bf1293d -r e0e769f3dfbd sys/kern/sys_ptrace_common.c
--- a/sys/kern/sys_ptrace_common.c      Wed May 01 15:17:49 2019 +0000
+++ b/sys/kern/sys_ptrace_common.c      Wed May 01 17:02:40 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_ptrace_common.c,v 1.50 2019/04/30 22:32:01 kamil Exp $     */
+/*     $NetBSD: sys_ptrace_common.c,v 1.51 2019/05/01 17:02:40 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 1.50 2019/04/30 22:32:01 kamil Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_ptrace_common.c,v 1.51 2019/05/01 17:02:40 kamil Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ptrace.h"
@@ -1246,6 +1246,21 @@
                        }
                }
 
+               /*
+                * If the address parameter is 0, report error.
+                *
+                * It's a popular mistake to set Program Counter to 0x0.
+                * In certain kernels this is allowable parameter and causes
+                * portability issue.
+                *
+                * Disallow explicitly zeroed PC, instead of triggering
+                * a harder to debug crash later.
+                */
+               if (addr == 0) {
+                       error = EINVAL;
+                       break;
+               }
+
                /* If the address parameter is not (int *)1, set the pc. */
                if ((int *)addr != (int *)1) {
                        error = process_set_pc(lt, addr);