Vulnerability Development: is this a bug ?

[Guy Cohen <guy () CRYPTO ORG IL>]

Hello,

first i mast explain i am no programmer, i just read a few documents
on the web and try to play with stuff. If this is inappropriate here
please tell me and except my apologize.

anyhow,
i have this asm code:

.global id
.global end
.data
id:
        jmp start
doit:
        popl %esi
        movl %esi,0x08(%esi)
        xorl %eax,%eax
        movb %eax,0x07(%esi)
        movl %eax,0xc(%esi)

        movb $0xb,%eax
        movl %esi,%ebx
        leal 0x8(%esi),%ecx
        xorl %edx,%edx
        int  $0x80

start:
        call doit
        .string "/bin/idX"
end:

and the c to run it:
extern void id();
extern void end();
main()
{
  id();
}

both a ripof from Marc Blumenauer <marc () system-security net>

but what strikes me odd is that if i cange any of the length of the string
to a wrong lenght (0x09 for example)  my cpu get to 98.8 usage % after 5
seconds. (this is run by regular user)

Can any one explain/verify this on a computer with more the 133MHz and 48 RAM ?


Cheers,

Guy