[8690] in bugtraq
Linux 2.0.36: The stuff that was 'fixed quietly' [Summary]
daemon@ATHENA.MIT.EDU (Alan Cox)
Thu Dec 10 21:59:42 1998
Date: Thu, 10 Dec 1998 22:50:00 GMT
Reply-To: Bugtraq List <BUGTRAQ@NETSPACE.ORG>
From: Alan Cox <alan@LXORGUK.UKUU.ORG.UK>
To: BUGTRAQ@NETSPACE.ORG
Linux 2.0.36 fixed various security holes as does any stable OS update. Some
of these may have equivalents in other systems, so this documents the
relevant ones now that every vendor should have their kernel updates long
out.
Overall:
o If you have untrusted local users using 2.0.x x<36 there are denial
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 change
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 partition
table with 65535 listed for cylinders caused divide by zero errors.
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 OS's
but I doubt the readv/fencepost errors have any obvious equivalence.
------
Vendor upgrade notes:
Red Hat Software:
http://www.redhat.com/support/docs/rhl/intel/kernel-upgrade-intel.html
No other vendor has bothered to reply to the original vendor-sec request
for comments on this message so far.
