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Update: Security Hole in Kernel Allows Privilege Extensions
Nov 04, 2009
A null-pointer dereference in the Linux kernel allows local users to assume root privileges. Brad Spengler, who claims first discovery, announced that he will present a corresponding exploit during the course of the day.
Concurrent with Spengler's discovery in mid-October, Earl Chew likewise brought attention to the bug in an lkml.org blog. The bug affects all kernel versions in the 2.6 series and was fixed in the upcoming 2.6.32 RC. So far Red Hat is the only distro providing patches for what is now the CVE-2009-3547 advisory. Users of other distros can apply a workaround that sets the pointer to a value higher than zero, which prevents the exploit. Admins can enter
# cat /proc/sys/vm/mmap_min_addr
to read the current pointer value. If larger than zero, no action need be taken, otherwise use the command
# sysctl -w vm.mmap_min_addr="4096"
to set the value to 4096, for example. The value, however, is only good until the next reboot. To give it a more lasting value, users of Debian or its derivatives should use the following commands:
First indications are that Ubuntu/Kubuntu 9.10 are not affected by the bug, because the initial counter is set to 65535. However, subsequently installed programs such as Wine or Qemu will reset the counter to zero. First tests with Wine installations show this to be evident. The openSUSE distro is potentially the most vulnerable in that the initial counter is also set to zero.
(Thomas Leichtenstern)
Comments
get root
phil
Nov 18, 2009 3:04am GMT
sudo -s
sudo echo
JR
Nov 10, 2009 10:54am GMT
You can't 'sudo echo > outputfile'. Then echo gets called with superuser privileges, but the actual output gets piped to outputfile with normal user privileges and fails.
The correct way would be to either use 'sudo -i' or 'sudo su' to enter a true root shell, or to use tee.
$ echo "vm.mmap_min_addr = 4096" | sudo tee /etc/sysctl.d/mmap_min_addr.conf
Add the argument -a to tee to make it append the echoed line to the end of the file. Merely using tee like above will replace the file if it exists with the new content.
Article update
Britta Wuelfing
Nov 10, 2009 9:49am GMT
Due to some formatting problems the commands have not been shown correctly as in the original article. The article has been updated. We apologize for the inconvinience!
The article on THIS page was incredibly disappointing because it assumes expert Linux terminal command knowledge. I literally wasted half an hour of my existence trying to figure out what I was doing wrong. Went to the site above, cut/paste x 2, done.
sudo
Alex
Nov 08, 2009 11:00pm GMT
Martini1179, try "sudo -i" and then enter those commands.
...and
Martini1179
Nov 08, 2009 9:05pm GMT
...and I checked the value and it IS at zero. I have Wine installed.
Terminal commands DO NOT work in Ubuntu Jaunty
Martini1179
Nov 08, 2009 9:03pm GMT
The terminal commands for the more permanent don't work in Ubuntu Jaunty. Whatever I do, I get a "permission denied" error, sudo or no sudo. It doesn't even ask for a sudo password.
Comments
get root
phil Nov 18, 2009 3:04am GMT
sudo -ssudo echo
JR Nov 10, 2009 10:54am GMT
You can't 'sudo echo > outputfile'. Then echo gets called with superuser privileges, but the actual output gets piped to outputfile with normal user privileges and fails.The correct way would be to either use 'sudo -i' or 'sudo su' to enter a true root shell, or to use tee.
$ echo "vm.mmap_min_addr = 4096" | sudo tee /etc/sysctl.d/mmap_min_addr.conf
Add the argument -a to tee to make it append the echoed line to the end of the file. Merely using tee like above will replace the file if it exists with the new content.
Article update
Britta Wuelfing Nov 10, 2009 9:49am GMT
Due to some formatting problems the commands have not been shown correctly as in the original article. The article has been updated. We apologize for the inconvinience!wrong code
Alex Nov 10, 2009 9:06am GMT
Please, remove <br> from codeecho "vm.mmap_min_addr = 4096" > /etc/sysctl.d/mmap_min_addr.conf<br>
/etc/init.d/procps restart
This tag doesn't allow to run commands in case of copy/paste in terminal.
If you have wine installed the instructions are a bit different
Kory Nov 09, 2009 11:13pm GMT
Check if you have a file here:/etc/sysctl.d/wine.sysctl.conf
If so, modify the statement in there from:
vm.mmap_min_addr = 0
to:
vm.mmap_min_addr = 1024
OR
vm.mmap_min_addr = 4096
Then run:
sudo /etc/init.d/procps restart
Then check it with the cat:
cat /proc/sys/vm/mmap_min_addr
Permanent fix in Ubuntu
David Waine Nov 09, 2009 10:54pm GMT
The permanent fix work in ubuntu but you need to get to a root terminal window:# sudo gnome-terminal
Then enter the commands in this new terminal.
Ubuntu/Debian NON-EXPERTS: For a quick and easy WORKING fix.....
Martini1179 Nov 09, 2009 11:44am GMT
Ubuntu/Debian non-admin, non-experts can go to:http://wiki.debian.org/mmap_min_addr
for well-written, working instructions.
The article on THIS page was incredibly disappointing because it assumes expert Linux terminal command knowledge. I literally wasted half an hour of my existence trying to figure out what I was doing wrong. Went to the site above, cut/paste x 2, done.
sudo
Alex Nov 08, 2009 11:00pm GMT
Martini1179, try "sudo -i" and then enter those commands....and
Martini1179 Nov 08, 2009 9:05pm GMT
...and I checked the value and it IS at zero. I have Wine installed.Terminal commands DO NOT work in Ubuntu Jaunty
Martini1179 Nov 08, 2009 9:03pm GMT
The terminal commands for the more permanent don't work in Ubuntu Jaunty. Whatever I do, I get a "permission denied" error, sudo or no sudo. It doesn't even ask for a sudo password.