Hello,
libguestfs has a guestmount command that basically gives access via fuse
to filesystem images. It also takes options for fuse.
When -o default_permissions is not given, the mounting user should have
full access to everything (he will have access to the image anyway). Of
course, it should also be possible to give -o default_permissions to
have the kernel check the permissions, which could be useful for some
use cases.
Now the strange thing is that the guestmount command implements the
access function in fuse_operations. This results in the following bug:
https://bugzilla.redhat.com/show_bug.cgi?id=1761563
I have been asked to ask here for clarification on certain points:
1) If the above behaviour is wanted (no access checks without "-o
default_permissions"; the expected checks by the kernel if the option is
given), what is the right way to implement it? Can the access function
be just omitted?
2) If so, in which use cases is the access function usually implemented?
Do I understand correctly that this is only in case some fuse clients
wants to implement some *own* particular access restrictions (for
whatever reason) when "-o default_permissions" is *not* given?
3) What could be the case why the access function was implemented in the
first place? Maybe someone from libguestfs knows this, but it have found
https://www.redhat.com/archives/libguestfs/2014-June/msg00080.html
where some problem is described when there is no access function.
D.H.