dl-load.c (ld.so) bug??

[Troy Benjegerdes]

On Mon, 21 Jun 1999, Hollis R Blanchard wrote:

> On Mon, 21 Jun 1999, Troy Benjegerdes wrote:
> > 
> > testcase:
> > 
> > #include <stdio.h>
> > int main(void){
> >         char * ptr;
> >         printf("hello world\n");
> >         fflush(stdout);
> >         ptr = (char *)malloc(100);
> >         free(ptr);
> > }   
> > 
> > 
> > compile this with:
> > gcc test.c -lefence -g -static
> > 
> > On a PPC glibc-2.1 box, this segfaults in dl-load.c:564
> > 
> > On a x86 Red Hat 6.0 system, it works fine (
> > [troybenj at mos6 troybenj]$ ./a.out
> > 
> >   Electric Fence 2.0.5 Copyright (C) 1987-1998 Bruce Perens.
> > hello world
> > [troybenj at mos6 troybenj]$ 
> > 
> > 
> > Either dl-load.c has a serious bug, or ElectricFence is broken on PPC.
> > I suspect it's the former, and if so, this would explain the weird
> > segfaults I've been seeing.
> > 
> > Can someone that knows glibc better please confirm or deny this for me?
> 
> Ok, I don't know squat about glibc, but doesn't the fact that it runs fine
> *without* Electric Fence indicate it's a problem with that?
> 
> -Hollis
> 

No. Electric Fence is designed to catch programming errors, such as
attempting to access memory which was not 'malloc'ed. I have traced this
down extensively a couple of months ago, and found that it does indeed
appear to overrun what it malloced.

In normal operation, if I am correct, the ld.so code is just silently
overwriting some other data. 

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| Troy Benjegerdes    |       troy at microux.com     |    hozer at drgw.net   |
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