Re: [RFC PATCH ghak100 V1 1/2] audit: avoid fcaps on MNT_FORCE

[Miklos Szeredi]

On Fri, Nov 16, 2018 at 6:34 PM Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
>
> Don't fetch fcaps when umount2 is called with MNT_FORCE to avoid a
> process hang while it waits for the missing resource to (possibly never)
> re-appear.

The patch would be pretty good if the dependence on MNT_FORCE wasn't
added.   As it is, it's buggy in more ways than one:

 - It does the opposite of the above (i.e. skips fcaps *unless*
MNT_FORCE is set)
 - sets LOOKUP_NO_REVAL from caller of path lookup, which is invalid
(LOOKUP_NO_REVAL is used only internally by path lookup)
 - the fact that *_path_mountpoint_at() shouldn't touch the mount root
is independent of MNT_FORCE

I still don't quite understand what audit is trying to do here, but
apparently it's okay to skip getxattr in the MNT_FORCE case.  So why
is it not okay to skip it in the non-MNT_FORCE case?

Thanks,
Miklos