[ast-developers] null pointer dereference in sh_assignok() function

[Tomas Klacko]

Hi,

I have a ksh script which causes null pointer
dereference in the sh_assignok() function a few
minutes after it is started. The script
is a bit elaborate and not mine.
Simply ignoring the NULL pointer seems to work:

<patch>
--- /dev/null    Fri Nov 29 06:35:21 2013
+++ new/components/ksh93/patches/17851169.patch    Fri Nov 29 06:35:20 2013
@@ -0,0 +1,30 @@
--- a/src/cmd/ksh93/sh/subshell.c
+++ b/src/cmd/ksh93/sh/subshell.c
@@ -234,15 +234,22 @@ Namval_t *sh_assignok(register Namval_t *np,int add)
 {
     register Namval_t    *mp;
     register struct Link    *lp;
-    register struct subshell *sp = (struct subshell*)subshell_data;
-    Shell_t            *shp = sp->shp;
-    Dt_t            *dp= shp->var_tree;
+    register struct subshell *sp;
+    Shell_t            *shp;
+    Dt_t            *dp;
     Namval_t        *mpnext;
     Namarr_t        *ap;
     int            save;
+
+        sp = (struct subshell*)subshell_data;
+
     /* don't bother with this */
-    if(!sp->shpwd || np==SH_LEVELNOD || np==L_ARGNOD || 
np==SH_SUBSCRNOD || np==SH_NAMENOD)
+    if(!sp || !sp->shpwd || np==SH_LEVELNOD || np==L_ARGNOD || 
np==SH_SUBSCRNOD || np==SH_NAMENOD)
         return(np);
+
+    shp = sp->shp;
+    dp = shp->var_tree;
+
     if((ap=nv_arrayptr(np)) && (mp=nv_opensub(np)))
     {
         shp->last_root = ap->table;

</patch>

Is the fix ok?

Tomas Klacko
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