[src/trunk]: src/sys/kern If no auxv is present, don't kmem_alloc(0). Easy to...

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

details:   https://anonhg.NetBSD.org/src/rev/7b8d073a2d37
branches:  trunk
changeset: 357864:7b8d073a2d37
user:      maxv <maxv%NetBSD.org@localhost>
date:      Thu Nov 30 18:44:16 2017 +0000

description:
If no auxv is present, don't kmem_alloc(0). Easy to panic the kernel by
typing 'cat /proc/aout_pid/auxv' on whatever a.out binary you're running.
Fortunately, amd64 does not enable EXEC_AOUT by default. Unfortunately,
i386 does enable it by default.

diffstat:

 sys/kern/kern_proc.c |  11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

diffs (40 lines):

diff -r 3aaccc394268 -r 7b8d073a2d37 sys/kern/kern_proc.c
--- a/sys/kern/kern_proc.c      Thu Nov 30 18:29:25 2017 +0000
+++ b/sys/kern/kern_proc.c      Thu Nov 30 18:44:16 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_proc.c,v 1.208 2017/11/07 19:44:04 christos Exp $ */
+/*     $NetBSD: kern_proc.c,v 1.209 2017/11/30 18:44:16 maxv Exp $     */
 
 /*-
  * Copyright (c) 1999, 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -62,7 +62,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_proc.c,v 1.208 2017/11/07 19:44:04 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_proc.c,v 1.209 2017/11/30 18:44:16 maxv Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_kstack.h"
@@ -2463,16 +2463,19 @@
        struct ps_strings pss;
        int error;
        void *uauxv, *kauxv;
+       size_t size;
 
        if ((error = copyin_psstrings(p, &pss)) != 0)
                return error;
+       if (pss.ps_envstr == NULL)
+               return EIO;
 
-       if (pss.ps_envstr == NULL)
+       size = p->p_execsw->es_arglen;
+       if (size == 0)
                return EIO;
 
        size_t ptrsz = PROC_PTRSZ(p);
        uauxv = (void *)((char *)pss.ps_envstr + (pss.ps_nenvstr + 1) * ptrsz);
-       size_t size = p->p_execsw->es_arglen;
 
        kauxv = kmem_alloc(size, KM_SLEEP);