On Tue, 2023-04-25 at 18:35 +0200, Marko Petrović wrote: > > It seems that _maybe_, similar to the 'hostfs' kernel argument, there > > should be a way to contain the set of options? > > > > What do I mean by that? I mean that today, the inside of the virtual > > machine (for lack of a better word) can only mount outside folders that > > are contained in the folder indicated by the 'hostfs' argument. > > Similarly, perhaps the "outside administrator" should be able to > > indicate that xattr permissions _must_ be used, or _must not_ be used? > Nice observation. It shouldn't be hard to do this, I can just change > the interpreted meaning of mnt_use_xattr and hostfs_fs_info->use_xattr > to comply with this behavior. Thanks for bringing this to attention. > > > > Which would imply a new kernel argument that can be configured to "force > > use", "force don't use" and "don't care", with perhaps even for backward > > compatibility the default being "force don't use"? > > > > Not sure. Anton? Richard? Any opinions?
> Maybe xattrperm and noxattrperm can be kernel command line arguments > used for "force use" and "force don't use" and when none is specified, > the behavior could be "don't care" which would thus be the default. Right. Actually now looking at this again, they should probably be flags inside the hostfs= argument? Like the "append" flag now. Not really sure what the default should be, perhaps it makes sense to not allow it by default so it's the same as now? But I don't know how strict we need to be about this. > That may also be reasonable for the purpose of backward compatibility > since the usage of extended attributes would then be specified as an mount > option and applications not aware of it would just use the old behavior > (since the extended attributes would be used only when specified in > mount options). Right. I was more thinking of the isolation aspects of this. > On the other hand, that would require a little different mounting of > root filesystem. Maybe adding rootxattrperm as a new kernel command line > argument for mounting root with "rootfstype=hostfs hostfs=rootxattrperm" > could be the solution (for when root should use extended attributes, but > the general behavior should still be "don't care")? > What are your opinions? Oh, that's a good point too. I don't think I have much of an opinion on it though. But yeah, why not have another flag "rootxattrperm" for the hostfs= option, along with xattrperm and noxattrperm (or allowxattrperm and forcexattrperm if we need noxattrperm to be the default per above.) johannes PS: Note that in uml/next my patches with the split are merged, so when you rebase please rebase on that and adjust accordingly with the exported symbol we discussed. _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um
