Messages in this thread | | | From | (Eric W. Biederman) | Subject | Re: [PATCH -mm 5/7] add user namespace | Date | Fri, 14 Jul 2006 10:13:47 -0600 |
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Kyle Moffett <mrmacman_g4@mac.com> writes:
> On Jul 14, 2006, at 10:17:28, Serge E. Hallyn wrote: >> Quoting Eric W. Biederman (ebiederm@xmission.com): >>> No. The uids in a filesystem are interpreted in some user namespace >>> context. We can discover that context at the first mount of the filesystem. >>> Assuming the uids on a filesystem are the same set of uids your process is >>> using is just wrong. >> >> But, when I insert a usb keychain disk into my laptop, that fs assumes the >> uids on it's fs are the same as uids on my laptop... >> >> Solving that problem is interesting, but may be something to work with a much >> wider community on. I.e. the cifs and nifs folks. I haven't even googled to >> see what they say about it. > > IMHO filesystems _and_ processes should be primary objects in a UID namespace. > This would make it possible to solve the usb-key problems _and_ the > user-mounted FUSE problems. If "ns0" is the boot uid namespace, then put the > freshly mounted USB key in a new "ns1" (names just for convenience). All the > user processes would continue to be in ns0, but with the kernel keyring system > you could create a new "uid" keytype and give the logged in user (ns0,user_uid) > a user-key with (ns1,0*). If you added bits to the user-keys to represent the > equivalent of CAP_DAC_OVERRIDE/CAP_CHOWN/etc for that process and UID > namespace, then the user could do anything to any file on their USB key, even > change ownership, without disrupting the rest of the system. Likewise, if you > did that for user FUSE filesystems, then suid binaries would not be able to get > themselves into trouble in exploitive FUSE infinitely-recursive monstrosities.
Thank you!
It is nice to see when someone else gets the point :)
I had not quite considered how that affects user mounted filesystems but that does look like a real solution.
Now we just need to implement these things and work out the details of user keys to map user ids.
Eric
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