"Permission denied" when echoing 0 to disable_modules

[Christoph]

Hello,

as root, I executed the command "echo 0 > /proc/sys/kernel/grsecurity/disable_modules" and got:

-su: /proc/sys/kernel/grsecurity/disable_modules: Permission denied

Syslog says:

grsec: denied modification of grsecurity sysctl value : disable_modules by /bin/bash[bash:10164] uid/euid:0/0 gid/egid:0/0, parent /bin/su[su:10162] uid/euid:0/0 gid/egid:0/0

What can be the reason for that?

All other grsecurity sysctl values can be changed.

Regards
Christoph