Re: Linux kernel sysctl() vulnerability

[Florian Weimer <Florian.Weimer () RUS UNI-STUTTGART DE>]

Chris Evans <chris () SCARY BEASTS ORG> writes:

> There exists a Linux system call sysctl() which is used to query and
> modify runtime system settings. Unprivileged users are permitted to query
> the value of many of these settings.

It appears that all current Linux kernel version (2.2.x and 2.4.x) are
vulnerable.  Right?

Was it really necessary to release this stuff just before the weekend?

The following trivial patch should fix this issue. (I wonder how you
can audit code for such vulnerabilities.  It's probably much easier to
rewrite it in Ada. ;-)

--- sysctl.c    2001/02/10 09:42:12     1.1
+++ sysctl.c    2001/02/10 09:42:26
@@ -1123,7 +1123,7 @@
                  void *oldval, size_t *oldlenp,
                  void *newval, size_t newlen, void **context)
 {
-       int l, len;
+       unsigned l, len;

        if (!table->data || !table->maxlen)
                return -ENOTDIR;

--
Florian Weimer                    Florian.Weimer () RUS Uni-Stuttgart DE
University of Stuttgart           http://cert.uni-stuttgart.de/
RUS-CERT                          +49-711-685-5973/fax +49-711-685-5898