CAP_LINUX_IMMUTABLE question

[Sean Hunter <sean@dev.sportingbet.com>]

Hi there

I am currently trying to tie down the capability bounding set on one of my
servers.  CAP_SYS_RAWIO and CAP_SYS_MODULE have been a great success (although
dropping CAP_SYS_RAWIO seems to prevent reading /proc/sys/kernel/cap-bound).

I now want to drop CAP_LINUX_IMMUTABLE, and have (I think) done that.  However,
it seems to make no difference to my ability to set or clear the immutable
attribute.  I tried this on ext2 and ext3 filesystems just to be on the safe
side.

[root@henry /boot]# lcap CAP_LINUX_IMMUTABLE
[root@henry /boot]# lsattr ./vmlinux-2.4.2-2smp
---i--------- ./vmlinux-2.4.2-2smp
[root@henry /boot]# chattr -i ./vmlinux-2.4.2-2smp
[root@henry /boot]# lsattr ./vmlinux-2.4.2-2smp
------------- ./vmlinux-2.4.2-2smp
[root@henry /boot]# chattr +i ./vmlinux-2.4.2-2smp
[root@henry /boot]# lsattr ./vmlinux-2.4.2-2smp
---i--------- ./vmlinux-2.4.2-2smp

I thought that giving up CAP_SYS_RAWIO may have forfeited my ability to drop
any further caps, so I rebooted and dropped CAP_SYS_MODULE and
CAP_LINUX_IMMUTABLE first, just to be on the safe side.  This made no visible
difference.

Am I doing anything obviously dumb?

Sean