Report from Martin Schwidefsky:
There is/has been a bug with copy_from_user on s390. The problem is that it does
not pad the kernel buffer with zeroes in case of a fault on the user address.
That allows a malicious user to read uninitialized kernel memory. The bug is
already fixed upstream:
Unfortunatly a bug crept into the bug fix for 2.4. The arguments of the mvcle
that is supposed to clear the kernel buffer have been swapped for 64 bit (the
code is fine for 31 bit).
A fix for this problem has just been committed to the RHEL3 E9
patch pool this evening (in kernel version 2.4.21-47.0.1.EL).
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.
A fix for this problem has also been committed to the RHEL3 U9
patch pool this evening (in kernel version 2.4.21-47.3.EL).