FreeBSD Security Advisory FreeBSD-SA-03:09.signal

[Jason Dambrosio]

On Sun, Aug 10, 2003 at 07:57:06PM -0700, FreeBSD Security Advisories wrote:
> II.  Problem Description
> 
> Some mechanisms for causing a signal to be sent did not properly
> validate the signal number, in some cases allowing the kernel to
> attempt to deliver a negative or out-of-range signal number.  Such
> errors were present in the ptrace(2) system call and the `spigot'
> video capture device driver.
> 
> The error in ptrace(2) was introduced in FreeBSD version 4.2-RELEASE
> (4-STABLE dated Oct 26 04:34:41 2000 UTC).

...

> IV.  Workaround
> 
> There is no workaround for the local denial-of-service attack.

    Wouldn't a possible workaround be, to load a kld module that would
replace the ptrace(2) system call with a patched one? I remember doing
such a trick for modifying other system calls using kld modules...

Jason