Red Hat Bugzilla – Bug 183416
DoS attack possible via nfsservctl
Last modified: 2007-11-30 17:07:23 EST
Description of problem:
There is a denial of service attack possible using the nfsservctl()
system call. When it is invoked with an incorrect version number in
the arguments, it prints a message and returns an error.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Invoke the nfsservctl() system with anything but 0x201 as the version
number in the first argument.
The kernel prints the message, "nfsd: incompatible version in syscall.",
and returns an error.
Just the error return.
Created attachment 125474 [details]
The solution is to not print the message. It is only of vague usefulness
Also cleaned up the error handling in the compat version of the nfsservctl()
system call. It was attempting to proceed, even if the attempts to copy in
the arguments from the user level had failed.
committed in stream U4 build 34.18. A test kernel with this patch is available
from http://people.redhat.com/~jbaron/rhel4/ However, there is a *serious* slab
corruption issue with this kernel, and thus it should not be released to
customers under any circumstances. I'll update this bug when the kernel is
We've identified the corruption as specfic to x86-64 smp kernel builds 34.16 and
34.17. All other builds are safe for consumption.
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.