Problemy z kernelem 2.2.19

W jądrze 2.2.19 występuje błąd związany z ptrace. Oprócz tego istnieje także możliwość wykonania lokalnego ataku DOS.

Aby jednak do tego nie doprowadzić, zalecany jest upgrade jądra. W tym celu Rafał Wojtczuk przygotował łatę, która naprawia występujący błąd, a całość jest dołączona do projektu OpenWalla.

Poniżej pełny opis błędu:

A new revision of the Openwall Linux kernel patch, 2.2.19-ow3, is now available. It contains fixes for two Linux kernel vulnerabilities discovered by Rafal Wojtczuk and is strongly recommended for use with Owl. One of the vulnerabilities affected SUID/SGID execution by processes being traced with ptrace(2). It was possible to trick the kernel into recognizing an unsuspecting SUID root program as the (privileged) tracer process. Then, if that program would execute a program supplied by the malicious user (with the user’s credentials), the user’s program would inherit the ability to trace. Fortunately, there’s no program that would meet all of the requirements for this attack in the default Owl install. However, certain supported non-default configurations of Owl are affected. In particular, if newgrp(1) is made available to untrusted users (which is a supported owl-control setting) or certain third-party software which contains SUID root binaries is installed, the vulnerability may become exploitable and result in a local root compromise. The other vulnerability allowed for an effective local DoS attack by causing the kernel to spend an almost arbitrary amount of time on dereferencing a single symlink, without giving a chance for processes to run.