Grsecurity/Application-specific Settings

The RBAC System Application-specific Settings Reporting Bugs

This page lists applications that need specific settings to work with grsecurity and PaX. If you wish to add an application to the list, you are most welcome to do so. Please keep the list in alphabetical order and remember to update the table of contents on the front page.

ATI Catalyst (fglrx) graphics driver edit

When using Xorg and the proprietary ATI Catalyst graphics driver, CONFIG_PAX_USERCOPY must not be set as PAX_USERCOPY prevents a real overflow from occurring in the ATI driver that is still unfixed. This is in addition to what's shown in the section on Xorg below.

As of 11.8, CONFIG_PAX_MEMORY_UDEREF must also be disabled.

cPanel jailshell edit

Because cPanel's jailshell needs to mount filesystems (including bind mounts) after chrooting, both chroot_caps (due to needing CAP_SYS_ADMIN) and chroot_deny_mount will need to be disabled. To do this, either disable the respective options in your kernel configuration (CONFIG_GRKERNSEC_CHROOT_CAPS and CONFIG_GRKERNSEC_CHROOT_MOUNT) or disable them in an init script if GRKERNSEC_SYSCTL is enabled. Use the following commands:

echo 0 > /proc/sys/kernel/grsecurity/chroot_caps
echo 0 > /proc/sys/kernel/grsecurity/chroot_deny_mount

We will be working with cPanel developers to see if the need for this workaround can be avoided in future jailshell versions.

Firefox (or Iceweasel in Debian) edit

Mozilla Firefox and possibly all, if not some(?) of, the files in the folder (/usr/lib/firefox) with the Firefox binary (called /usr/lib/firefox/firefox) need mprotect disabled for flash to function. Without the Firefox binary having disabled mprotect Firefox will enter an infinite loop at startup or take minutes to load. Without the files having mprotect disabled any page encountered with Flash will surely run an infinite loop and the Firefox process will have to be killed.

The option must be disabled for just-in-time compilation of certain scripts for both xulrunner-stub and xulrunner-bin. See Grsecurity forums for more details. [1] The safest option would of course be denying mprotect and boycot sites that use just-in-time (JIT) flash scripts. You may disable JIT compilation in the browser by initiating the address about:config, search for "jit" in the page's integrated search bar, and double-click the options "" and "javascript.options.methodjit.content" to set them to "false".

Firefox >= 3.5 may need RANDMMAP to be disabled (), if not it will enter in an infinite loop during startup. To disable, execute paxctl -r /firefox_binary. Usually the binary is somewhere in /usr/lib64/*firefox*. See for more details. As of at least Firefox 13 on Ubuntu-based distros you can enable RANDMMAP.

Google Chrome 15.0.874.106 edit

On Google Chrome:

$ paxctl -v /opt/google/chrome/chrome
PaX control v0.5
Copyright 2004,2005,2006,2007 PaX Team <>
- PaX flags: P----m-x-eR- [/opt/google/chrome/chrome]
	PAGEEXEC is enabled
	MPROTECT is disabled
	RANDEXEC is disabled
	EMUTRAMP is disabled
	RANDMMAP is enabled

$ paxctl -v /opt/google/chrome/nacl_helper
PaX control v0.5
Copyright 2004,2005,2006,2007 PaX Team <>
- PaX flags: -p---m-x-e-- [/opt/google/chrome/nacl_helper]
	PAGEEXEC is disabled
	MPROTECT is disabled
	RANDEXEC is disabled
	EMUTRAMP is disabled

$ paxctl -v /opt/google/chrome/chrome-sandbox 
PaX control v0.5
Copyright 2004,2005,2006,2007 PaX Team <>
- PaX flags: -----m-x-e-- [/opt/google/chrome/chrome-sandbox]
	MPROTECT is disabled
	RANDEXEC is disabled
	EMUTRAMP is disabled

These PaX flags work well on my system with flash. Chrome's nacl does throw this however:

[] Bad NaCl helper startup ack (0 bytes)

Grub edit

Grub uses nested functions and thus needs either PAX_EMUTRAMP enabled in the kernel and EMUTRAMP enabled on affected binaries, or if PAX_EMUTRAMP is not enabled in the kernel, needs MPROTECT disabled on affected binaries. Depending on the version of grub in use, some of the following files may not exist, but you should mark all those that exist. To add EMUTRAMP, use the '-CE' argument to paxctl. To remove MPROTECT, use '-Cm'.


GUFW/UFW firewalls or Update Manager edit

GUFW is an optional graphical application interface for the Ubuntu firewall (UFW), both of which use Python. Update Manager is a Gnome application for updating packages that also depends on Python. Really, any application that uses Python try enabling EMUTRAMP for the version of Python that is the dependency of your affected program (GUFW or Update Manager). (Example: # paxctl -E /usr/bin/Python2.7).

IOQuake3 edit

Ioquake3 requires disabling mprotect restrictions to run correctly.

ISC DHCP Server edit

NOTE: grsecurity patches released as of May 4th, 2014 do not require the below modifications

On some systems, after upgrading to a grsecurity-enabled kernel with GRKERNSEC_PROC_USERGROUP enabled, the kernel log may be spammed with:

init: isc-dhcp-server main process ended, respawning
init: isc-dhcp-server main process (pid) terminated with status            1

This may be due to unprivileged users not having access to /proc/net/dev as this dhcpd requires. You can confirm by running dhcpd -f from the command-line, which should display the following error:

Error opening '/proc/net/dev' to list interfaces

To fix this, grep your kernel config for CONFIG_GRKERNSEC_PROC_GID, then add a group for that gid to /etc/group if it doesn't already exist. Then add dhcpd to that group. The added line will look similar to:


As the DHCP server is continually attempting to respawn, upon making this change you should find it running properly.

Java edit

With problems with an epoll stack trace lookup [2]. Also there is a problem with just-in-time compilation. Disable mprotect for /usr/lib/jvm/java-6-sun- and /usr/lib/jvm/java-6-sun-

Nagios edit

Nagios needs to be able to view all processes on the system in order to accurately portray service status and performance statistics. It must therefore be run with the group of the CONFIG_GRKERNSEC_PROC_GID you configured, or as set with the grsec_proc_gid kernel command-line option.

Node.js edit

Node.js needs to execute arbitrary code at runtime. To permit this, mprotect needs to be disabled. On most systems, this can be accomplished with the command:

paxctl -Cm /usr/bin/nodejs

Note: For certain apps like electron, you will need to disable mprotect for both the electron and nodejs executables edit uses two binaries which need custom settings to work. Both /usr/lib/openoffice/program/soffice.bin and /usr/lib/openoffice/program/unopkg.bin need to have unrestricted mprotect. [3] edit

the same as, but need to have unrestricted mprotect for:

/usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java to work if you use libreoffice-base: Database.

PHP and other applications that set their own resource limits edit

While Apache/PHP run very well with a grsec/PaX enabled kernel, you could feel like there are possible memory leaks or strange OOM (out of memory) errors with PHP using a PaX enabled kernel with the SEGMEXEC flag enabled. There's no memory leak, and the OOM errors are normal, particularly if you didn't set high enough resource limits.

Concerning "abnormal" memory usage with PHP and SEGMEXEC flag enabled, see spender's answers on comments:

"Due to VMA mirroring, the SEGMEXEC option causes accounted vm usage to double.  So you weren't 
experiencing a memory leak -- you were just being accounted for twice as much memory as you 
thought you were using. The solution would be to double the resource limit or, if your system
is NX-capable and PAE is enabled, use PAGEEXEC." edit might need some specific kernel settings during configuration (depending on the hardware and the drivers used X won't run with non-executable pages (PAX_NOEXEC)). The problem manifested especially in XFree4. Although, recent versions of are known to work with non-executable pages enabled. If you run into problems with X watch your non-executeble settings.

Some users experience mouse freezes when the system load is high. Typically the mouse pointer is reset, but stays in the upper left corner of the screen. This behaviour was found to occur with certain pre-emption settings [4][5]. It seems to be an interaction between forced-preemption and KERNEXEC. You should be able to re-enable KERNEXEC as long as you disable preemption or use voluntary preemption.

According to the Pax-Team KERNEXEC should work as is, since the changes should be only basic functions like open/close functions. If you should experience problems switch to voluntary or none pre-emption.

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