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2.0.36 Kernel (was:isdnutils and 2.0.36 (was: Linux 2.0.36 in slink?))

On Wed, 16 Dec 1998, Remco Blaakmeer wrote:

> On Wed, 16 Dec 1998, Enrique Zanardi wrote:
> > On Tue, Dec 15, 1998 at 01:21:52PM -0800, Oscar Levi wrote:
> > > It is unwise to change the kernel just before we ship.  I support
> > > making it optional for the minority of people who use ISDN adaptors.
> > 
> > And what about the "minority of people" that care about security holes in
> > our default 2.0.35 kernel?
> Those people compile their own kernels anyway. :-)
> How many people would be opposed to including a kernel-source package for
> the 2.0.36 kernel, leaving 2.0.35 the 'standard' kernel for slink? I don't
> think it would break anything, and compiling your own kernel really isn't
> that hard anymore.

Personally I think it is absolutly necessary to have 2.0.36 in slink:

>From Linux Weekly News:

       Although the release of the 2.0.36 version
       of the Linux kernel is not new, many
       people are unaware of the security
       improvements made available in 2.0.36.
       Alan Cox posted a note with a short list of
       security improvements. Notably, it is less
       vulnerable to Denial-of-Service attacks
       and a potentially exploitable crash related
       to IP Masquerading has been repaired. 

And this is Alan Cox' note:

Date:   Thu, 10 Dec 1998 22:50:00 GMT
From:   Alan Cox <alan@LXORGUK.UKUU.ORG.UK>
Subject:      Linux 2.0.36: The stuff that was 'fixed quietly' [Summary]

Linux 2.0.36 fixed various security holes as does any stable OS update.
of these may have equivalents in other systems, so this documents the
relevant ones now that every vendor should have their kernel updates long


o       If you have untrusted local users using 2.0.x x<36 there are 
        of service attacks possible. If you actively use securelevel and
        append only files there is a possibility to write data over files
        a user has only append access too.

o       If you run masquerading there is a possible crash mended. I failed
        to succeed in causing it but its fixed nevertheless and its
        potentially exploitable.

The things of relevance we fixed

o       mmap on append only files has to be restricted to read maps. Linux
        2.0.35 did this but it was possible to use mprotect() to then
        the mapping to Read/write. 2.0.36 closes this hole.

o       readv/writev could crash. Linux uses "NULL" to indicate no method
        is available for unix read/write operations. The readv/writev
        calls neglected to check this. So a writev() to a device that has
        no write method crashes the program and may make a mess.

o       A fencepost error in the syscall return path. x86 syscall returns
        are fun because many things can fault in supervisor space if the
        user process did something stupid, or another thread does things
        like play with the local descriptor table between the call and
        return. The Linux kernel catches such faults and tidies up. There
        was a small range of code that it mistakenly considered as not
        part of the return path.

o       When interpreting PC partition tables there are a couple of places
        where you end up doing (something+1) and dividing by it. A
        table with 65535 listed for cylinders caused divide by zero

o       An unchecked size/offset assumption in the masquerading code could
        in theory lead to a crash.

I wouldnt be suprised to see the mmap and partition table ones in other
but I doubt the readv/fencepost errors have any obvious equivalence.

Heute ist nicht alle Tage, ich komme wieder, keine Frage!!!


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