Re: [RFC][PATCH 00/10] Mount, FS, Block and Keyrings notifications [ver #3]

From: Andy Lutomirski
Date: Thu Jun 06 2019 - 18:46:20 EST

> On Jun 6, 2019, at 3:38 PM, David Howells <dhowells@xxxxxxxxxx> wrote:
> Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>> I mean: are there cases where some action generates a notification but does
>> not otherwise have an effect visible to the users who can receive the
>> notification. It looks like the answer is probably ânoâ, which is good.
> mount_notify(). You can get a notification that someone altered the mount
> topology (eg. by mounting something). A process receiving a notification
> could then use fsinfo(), say, to reread the mount topology tree, find out
> where the new mount is and wander over there to have a look - assuming they
> have the permissions for pathwalk to succeed.

They can call fsinfo() anyway, or just read /proc/self/mounts. As far as Iâm concerned, if you have CAP_SYS_ADMIN over a mount namespace and LSM policy lets you mount things, the of course you can get information to basically anyone who can use that mount namespace.