[PATCH v6 23/40] exec: handle idmapped mounts

[Christian Brauner]

On Mon, Jan 25, 2021 at 11:03:16AM -0600, Serge Hallyn wrote:
> On Mon, Jan 25, 2021 at 05:44:04PM +0100, Christian Brauner wrote:
> > On Mon, Jan 25, 2021 at 10:39:01AM -0600, Eric W. Biederman wrote:
> > > Christian Brauner <christian.brauner at ubuntu.com> writes:
> > > 
> > > > When executing a setuid binary the kernel will verify in bprm_fill_uid()
> > > > that the inode has a mapping in the caller's user namespace before
> > > > setting the callers uid and gid. Let bprm_fill_uid() handle idmapped
> > > > mounts. If the inode is accessed through an idmapped mount it is mapped
> > > > according to the mount's user namespace. Afterwards the checks are
> > > > identical to non-idmapped mounts. If the initial user namespace is
> > > > passed nothing changes so non-idmapped mounts will see identical
> > > > behavior as before.
> > > 
> > > This does not handle the v3 capabilites xattr with embeds a uid.
> > > So at least at that level you are missing some critical conversions.
> > 
> > Thanks for looking. Vfs v3 caps are handled earlier in the series. I'm
> > not sure what you're referring to here. There are tests in xfstests that
> > verify vfs3 capability behavior.
> 
> *just* to make sure i'm not misunderstanding - s/vfs3/v3/ right?

Yes, in my mind it's always as "vfs v3 caps -> vfs3 caps". Sorry for the
confusion.