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: http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=52149ba6b0ddf3e9d965257cc0513193650b3ea8
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. http://rhn.redhat.com/errata/RHSA-2006-0710.html
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).