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SubjectRe: Upstream first policy

Weird. Somehow I only got a copy of this from lkml.

Alan Cox <> writes:

>> time. If pathnames were not fundamentally important we could apply
>> a patch like the one below and allow unprivileged users to unshare
>> the mount namespace and mount filesystems wherever. There is nothing
>> fundamental about those operations that require root privileges except
>> that you are manipulating the pathnames of objects.
> And in a purely SELinux enviromnment your patch would work out because
> you could use labels to control this stuff.
>> - if (!capable(CAP_SYS_ADMIN))
>> - return -EPERM;
>> -
> It does raise the question about whether you can do it if you had a
> namespace property of "ignore suidness". I'm not sure thats enough
> however.

The long term plan is to change that to.

if (nscapable(mnt_ns->user_ns, CAP_SYS_ADMIN))
return -EPERM.

That is.
- Create a new user/credential namespace (ultimately an unprivileged operation).
- Have the root user of the new user namespace create a new mount namespace.
- Over that new mount namespace the root user of the new user namespace
has full control.

It is a little convoluted but it maintains backwards compatibility. Unfortunately
there is still a long ways to go before we get there.


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