[PATCH] Segmentation fault when using the completion for interpreter

[PATCH] Segmentation fault when using the completion for interpreter

[Denis PILAT]

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I found a bug in gdb: when using the completion after the cli command
"interpreter-exec", an out-of-bound access occures.

Attached is a patch proposal that fixes it.

There were 2 problems in the original code in file interps.c, function 
interpreter_completer:
- the case of (num_matches == alloced) was not handled. In that case the 
matches list it not terminated by NULL.
- the xrealloc done at the end is useless since the num_matches is 
always <= alloced.

-- 
Denis PILAT


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2006-07-12  Denis PILAT  <denis.pilat@st.com>

	* interps.c (interpreter_completer): Allocate one more item to the
	'matches' list and set them all to 0 with a xcalloc.

[-- Attachment #3: interps.c.patch --]
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Index: interps.c
===================================================================
--- interps.c	(revision 486)
+++ interps.c	(working copy)
@@ -424,10 +424,11 @@ interpreter_completer (char *text, char 
   struct interp *interp;
 
   /* We expect only a very limited number of interpreters, so just
-     allocate room for all of them. */
+     allocate room for all of them plus one for the last that must be NULL
+     to correctly end the list. */
   for (interp = interp_list; interp != NULL; interp = interp->next)
     ++alloced;
-  matches = (char **) xmalloc (alloced * sizeof (char *));
+  matches = (char **) xcalloc (alloced + 1, sizeof (char *));
 
   num_matches = 0;
   textlen = strlen (text);
@@ -460,12 +461,6 @@ interpreter_completer (char *text, char 
       xfree (matches);
       matches = NULL;
     }
-  else if (num_matches < alloced)
-    {
-      matches = (char **) xrealloc ((char *) matches, ((num_matches + 1)
-						       * sizeof (char *)));
-      matches[num_matches] = NULL;
-    }
 
   return matches;
 }

Re: [PATCH] Segmentation fault when using the completion for interpreter

[Daniel Jacobowitz]

On Wed, Jul 12, 2006 at 04:02:18PM +0200, Denis PILAT wrote:
> 2006-07-12  Denis PILAT  <denis.pilat@st.com>
> 
> 	* interps.c (interpreter_completer): Allocate one more item to the
> 	'matches' list and set them all to 0 with a xcalloc.

Thanks!  This is OK.

-- 
Daniel Jacobowitz
CodeSourcery

Re: [PATCH] Segmentation fault when using the completion for interpreter

[Andrew STUBBS]

Daniel Jacobowitz wrote:
> On Wed, Jul 12, 2006 at 04:02:18PM +0200, Denis PILAT wrote:
>> 2006-07-12  Denis PILAT  <denis.pilat@st.com>
>>
>> 	* interps.c (interpreter_completer): Allocate one more item to the
>> 	'matches' list and set them all to 0 with a xcalloc.
> 
> Thanks!  This is OK.

I have committed this on behalf of Denis.

Andrew

Re: [PATCH] Segmentation fault when using the completion for interpreter

[Joel Brobecker]

> > 	* interps.c (interpreter_completer): Allocate one more item to the
> > 	'matches' list and set them all to 0 with a xcalloc.
> 
> Thanks!  This is OK.

Given that the next major release is scheduled for Nov/Dec, how about
putting this in the branch? Perhaps making a GDB 6.5.1 release in the
interim would make sense? There is another patch that caught my
attention:

        http://www.sourceware.org/ml/gdb-patches/2006-07/msg00133.html
        [patch] Fix gdb crash on some missing ELF debug info

-- 
Joel

Re: [PATCH] Segmentation fault when using the completion for interpreter

[Denis PILAT]

Ok, I'll have the interp.c patch commited in the branch.

Denis

Joel Brobecker wrote:

>>>	* interps.c (interpreter_completer): Allocate one more item to the
>>>	'matches' list and set them all to 0 with a xcalloc.
>>>      
>>>
>>Thanks!  This is OK.
>>    
>>
>
>Given that the next major release is scheduled for Nov/Dec, how about
>putting this in the branch? Perhaps making a GDB 6.5.1 release in the
>interim would make sense? There is another patch that caught my
>attention:
>
>        http://www.sourceware.org/ml/gdb-patches/2006-07/msg00133.html
>        [patch] Fix gdb crash on some missing ELF debug info
>
>  
>

Re: [PATCH] Segmentation fault when using the completion for interpreter

[Andrew STUBBS]

Joel Brobecker wrote:
>>> 	* interps.c (interpreter_completer): Allocate one more item to the
>>> 	'matches' list and set them all to 0 with a xcalloc.
>> Thanks!  This is OK.
> 
> Given that the next major release is scheduled for Nov/Dec, how about
> putting this in the branch? Perhaps making a GDB 6.5.1 release in the
> interim would make sense? There is another patch that caught my
> attention:
> 
>         http://www.sourceware.org/ml/gdb-patches/2006-07/msg00133.html
>         [patch] Fix gdb crash on some missing ELF debug info
> 

I have put Denis' patch in the 6.5 branch as requested.

Andrew