Andrea Arcangeli wrote:
the ability to disable KSM. That seems like a security concern to me since
registering a memory region ought to be an unprivileged action whereas
enabling/disabling KSM ought to be a privileged action.
sysfs files would then only be writeable by admin, so if we want to
allow only admin to start/stop/tune ksm it'd be enough to plug an
admin capability check in the ioctl to provide equivalent permissions.
Caps are not very granular unless you introduce a new capability.
Furthermore, it's a bit more difficult to associate a capability with a
user/group.
With sysfs, you use file based permissions to control the API. It also
fits into things like selinux a lot better.
In the very least, if you insist on not using sysfs, you should have a
separate character device that's used for control (like /dev/ksmctl).
Regards,
Anthony Liguori
I could imagine converting the enable/pages_to_scan/sleep_time to
module params and tweaking them through /sys/module/ksm/parameters,
but for "enable" to work that way, we'd need to intercept the write so
we can at least weakup the kksmd daemon, which doesn't seem possible
with /sys/module/ksm/parameters, so in the end if we stick to the
ioctl for registering regions, it seems simpler to use it for
start/stop/tune too.
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