Re: [RFC][PATCH 0/8] Mount, FS, Block and Keyrings notifications [ver #2]

On Tue, Jun 4, 2019 at 1:39 PM David Howells [off-list ref] wrote:

Andy Lutomirski [off-list ref] wrote:

quoted

quoted

Here's a set of patches to add a general variable-length notification queue
concept and to add sources of events for:

I asked before and didn't see a response, so I'll ask again.  Why are you
paying any attention at all to the creds that generate an event?

Casey responded to you.  It's one of his requirements.

It being a "requirement" doesn't make it okay.

However, the LSMs (or at least SELinux) ignore f_cred and use current_cred()
when checking permissions.  See selinux_revalidate_file_permission() for
example - it uses current_cred() not file->f_cred to re-evaluate the perms,
and the fd might be shared between a number of processes with different creds.

That's a bug.  It's arguably a rather severe bug.  If I ever get
around to writing the patch I keep thinking of that will warn if we
use creds from invalid contexts, it will warn.

Let's please not repeat this.