Re: Sodipodi 0.34 on Amd64 crashes on startup

Hello!

Thomas kirjutas R, 13.02.2004 kell 20:21:
> My first try:
> 
> $ gdb /usr/local/bin/sodipodi
> GNU gdb 5.3-26mdk (Mandrake Linux)
> Copyright 2002 Free Software Foundation, Inc.
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> This GDB was configured as "amd64-mandrake-linux-gnu"...
> (gdb) run
>         Keeping /usr/local/bin/sodipodi...
> Starting program: /usr/local/bin/sodipodi
> [New Thread 16384 (LWP 31140)]
>  
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 16384 (LWP 31140)]
> nr_svp_from_svl (svl=0x0, flat=0x0) at nr-svp.c:74
> 74              svp->length = nsegs;
> (gdb)
> 
> Does this give a clue as to where?

I do not know exactly where, but I know now why :-)

The bad piece of code is:

svp = malloc (sizeof (NRSVP) + (nsegs - 1) * sizeof (NRSVPSegment));

signed/unsigned mix. The bad thing happens, if nsegs = 0, i.e.
(nsegs - 1) = -1
As integers are 32 bit by default, 32-bit (-1) gets extended to
some very big number on 64-bit machine doing pointer arithmetic, 
resulting in try to allocate aroung 68GiB. It fails, of course, 
resulting NULL dereference in following line.

I'll try to prepare a patch and send it to list before tomorrow.

Best wishes,
Lauris Kaplinski





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