Mail Archives: cygwin/1997/11/07/22:57:58
On Fri, 7 Nov 1997, Tim Iverson wrote:
> Just to keep everyone from getting too scared, this really would only matter
> for secure sites with multiple users -- that particular sequence is a
> nonsense instruction. The only folks using it would be those deliberately
> wanting to bring the system down.
Well, I'd consider it a pretty big bug, especailly because anybody can run
it, if they can run binary files. For instance, if my ISP used a P5 for
their mail server, I could use procmail to freeze it, forcing some sort of
[expensive] intervention. Or, trojan horses *yikes*. I can see it now.
warez4free.exe... If NTFS partitions could be mounted async (or damaged
similarly from a power cycle without proper shut down), problems could
arise. The only people really exploiting the NetBIOS OOB bug would be
people trying to down a system too.. (didn't stop many people) :/
> Here it is decoded: lock cmpxchg8b eax
>
> BTW, I haven't tested it, so I don't know if this is even true. It should
> generate an illegal instruction exception, since the operand needs to be a
> memory reference.
Yes, it worked for me, all too well (not tested under 95). There was a
small rumor circulating on the FreeBSD-Current list that CPUs with >=12
stepping and 0x52c ids would be immune (doesn't seem to be true, for me).
gcc compiled the code (that I got my hands on) flawlessly, spitting out
only a warning.
- alex
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