linux-kernel - Re: [patch 1/8] add user mounts to the kernel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <E1HfX4D-0004H9-00@dorka.pomaz.szeredi.hu>
Date:	Sun, 22 Apr 2007 10:05:05 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	ebiederm@...ssion.com
CC:	miklos@...redi.hu, akpm@...ux-foundation.org, serue@...ibm.com,
	viro@....linux.org.uk, linuxram@...ibm.com,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	containers@...ts.osdl.org
Subject: Re: [patch 1/8] add user mounts to the kernel

> >> > +	if (mnt->mnt_flags & MNT_USER)
> >> > +		seq_printf(m, ",user=%i", mnt->mnt_uid);
> >> How about making the test "if (mnt->mnt_user != &root_user)"
> >
> > We don't want to treat root_user special.  That's what capabilities
> > were invented for.
> 
> For the print statement?  What ever it is minor.

It is a user interface, not a print statement.  Your suggested change
would be vetoed by any number of people.  

So either we have all mounts having owners, AND have /proc/mounts add
"user=0" to all mounts.  While I don't _think_ this would actually
break userspace, it would definitely make people complain.

The other choice is what the current patchset does: is to have
"legacy" mounts without owners, and "new generation" mounts with
owners having "user=UID" in /proc/mounts, regardless of the value of
UID.

> So I want to minimize the changes needed to existing programs.
> Now if all we have to do is specify MS_SETUSER when root a
> user with CAP_SETUID is setting up a mount as a user other
> then himself then I don't much care.  If we have to call MS_SETUSER
> as unprivileged users

You don't.  Unprivileged mounts _imply_ MS_SETUSER.

> >> > +
> >> > +	uid_t mnt_uid;			/* owner of the mount */
> >> 
> >> Can we please make this a user struct.   That requires a bit of
> >> reference counting but it has uid namespace benefits as well
> >> as making it easy to implement per user mount rlimits.
> >
> > OK, can you ellaborate, what the uid namespace benifits are?
> 
> In the uid namespace the comparison is simpler as are the propagations
> rules.  Basically if you use a struct user you will never need to
> care about a uid namespace.  If you don't we will have to tear through
> this code another time.

Well, OK.  I'll do the user_struct thing then.

Miklos
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/