Re: [PATCH] debugfs: fix security_locked_down() call for SELinux

On Fri, May 07, 2021 at 02:03:04PM +0200, Greg Kroah-Hartman wrote:

On Fri, May 07, 2021 at 01:41:50PM +0200, Ondrej Mosnacek wrote:

quoted

Make sure that security_locked_down() is checked last so that a bogus
denial is not reported by SELinux when (ia->ia_valid & (ATTR_MODE |
ATTR_UID | ATTR_GID)) is zero.

Why would this be "bogus"?

I presume selinux is logging a denial ... but we don't then actually
deny the operation.

quoted

Note: this was introduced by commit 5496197f9b08 ("debugfs: Restrict
debugfs when the kernel is locked down"), but it didn't matter at that
time, as the SELinux support came in later.

Fixes: 59438b46471a ("security,lockdown,selinux: implement SELinux lockdown")

What does this "fix"?

What is happening in selinux that it can not handle this sequence now?
That commit showed up a long time ago, this feels "odd"...

thanks,

greg k-h