On Mon, 2018-02-05 at 15:41 +0100, Julian Andres Klode wrote:
> On Mon, Feb 05, 2018 at 02:53:07PM +0100, Martin Wilck wrote:
> > On Mon, 2018-02-05 at 11:45 +0100, Julian Andres Klode wrote:
> > > On Mon, Feb 05, 2018 at 11:32:13AM +0100, Martin Wilck wrote:
> > > > On Mon, 2018-02-05 at 09:58 +0100, Julian Andres Klode wrote:
> > > > > C
> > > > > close (fd);
> > > > >
> > > > > - if (0 == strcmp(filename, loopinfo.lo_name))
> > > > > {
> > > > > + if (0 == strcmp(filename, loopinfo.lo_name)
> > > > > ||
> > > > > + 0 == strcmp(rfilename, loopinfo.lo_name)
> > > > > ||
> > > > > + (realpath(loopinfo.lo_name,
> > > > > rloopfilename)
> > > > > &&
> > > > > + 0 == strcmp(rfilename, rloopfilename)))
> > > > > {
> > > > > found = realpath(path, NULL);
> > > > > break;
> > > > > }
> > > >
> > > > That "if x matches y or x matches y' or x' matches y" feels
> > > > like
> > > > guesswork. Can't we simply call realpath() on both
> > > > loopinfo.lo_name
> > > > and
> > > > filename, and compare the two?
> > >
> > > Probably yes. That said there might be some corner cases:
> > >
> > > (1) What happens if the backing file of a loopback is deleted -
> > > realpath
> > > can fail with ENOENT.
> > > (2) A path could be longer than PATH_MAX and it would fail with
> > > ENAMETOOLONG
> > > - this is a "problem" with the initial realpath as well, but
> > > less
> > > so, because
> > > the user can control that.
> >
> > Both are scenarios in which kpartx would have good reason to fail
> > (with
> > a meaningful error message). That's better than guessing, IMO.
>
> (1) Definitely not. Just because one of your (potentially other)
> loopback devices
> has a deleted file you should not fail.
Sorry for being imprecise. You're right, aborting here while scanning
for a matching device would of course be wrong. And deleting such a
broken loop device can't be a big mistake.
> (2) I don't really know.
>
> But the problem here is that you are looking at loopback devices
> created by
> stuff other than kpartx, and they might not be in a "good" state. But
> you
> don't want to abort just because some _other_ loopback device is
> broken.
Can we agree on the following:
1 if realpath (filename) results in error, abort
2 if realpath(lo_name) results in ENODEV and filename matches lo_name,
remove loop device
3 if realpath(lo_name) results in another error code, skip it
4 remove if realpath(filename) matches realpath(lo_name)
???
Martin
--
Dr. Martin Wilck <mwilck@xxxxxxxx>, Tel. +49 (0)911 74053 2107
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
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