Messages in this thread | | | From | (Eric W. Biederman) | Subject | Re: [PATCH -mm 5/7] add user namespace | Date | Fri, 14 Jul 2006 12:40:05 -0600 |
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Trond Myklebust <trond.myklebust@fys.uio.no> writes:
> On Fri, 2006-07-14 at 11:36 -0600, Eric W. Biederman wrote: >> Dave Hansen <haveblue@us.ibm.com> writes: >> >> > On Fri, 2006-07-14 at 12:08 -0500, Serge E. Hallyn wrote: >> >> yes, of course, vfsmount, which I assume is what Eric meant? >> >> >> >> Which means we'd have to do this at permission() using the nameidata, or >> >> pass nd to generic_permission. >> > >> > Yeah, I think so. But, this is well into Al territory, and there might >> > be a better way. >> >> Well until we get that sorted out I will keep picking on i_sb. > > Don't bother: labelling superblocks with process-specific data is always > going to be unacceptable.
It's not process specific data. It is a pointer to global context in which uid's on the filesystem uniquely specify a user. This is something that would get set when the filesystem is mounted.
> In order to avoid aliased superblocks, you would have to be able > guarantee to be the sole owner of the data on the device that it refers > to. You'd have to own the device in order to do that, in which case you > are better off just labelling the device instead.
Now I do agree if I can set the information in vfsmount and not in the superblock it is probably better. But even with nfs mount superblock collapsing (which I almost understand) I don't see it as a real problem, as long as I could prevent the superblock from collapsing.
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