full-disclosure - Re: new class of printf issue: int overflow

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Message-Id: <200701111344.34704.mdontu@bitdefender.com>
Date: Thu, 11 Jan 2007 13:44:34 +0200
From: Mihai Dontu <mdontu@...defender.com>
To: full-disclosure@...ts.grok.org.uk
Subject: Re: new class of printf issue: int overflow

On Thursday 11 January 2007 03:00, Felix von Leitner wrote:
>   $ cat > t.c
>   #include <stdio.h>
>
>   int main() {
>     printf("%d\n",snprintf(0,0,"%*d %*d",0x40000000,1,0x40000000,1));
>   }
>   $ gcc -o t t.c
>   $ ./t
>   -2147483647
>   ./t  17.02s user 0.03s system 99% cpu 17.161 total
>   $
>
> the second line comes from my zsh, and as you can see running this
> program took 17 seconds.  top shows that the process used 1 gig of
> memory while it ran. :-)

  This is a pretty neat trick :)

  However, it takes ~1GB of virtual memory, which in Linux land is not a 
biggie if you don't write anything in it.
  Out of curiosity, I made the same test on Windows (cl.exe). It took ~14s to 
run, but it did not go above 300KB of memory usage.

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