(cutting out lists from CC) > > > > Your patch is changing the API in a very unsafe way, since there will > > > > be no error or warning on an unconverted fs. And that could lead to > > > > security holes. > > > > > > > > If we would rename the setattr method to setattr_new as well as > > > > changing it's behavior, that would be fine. But I guess we do not > > > > want to do that. > > > > > > Which "unconverted fses"? If we're talking out of tree stuff, then too > > > bad: it is _their_ responsibility to keep up with kernel changes. > > > > It is usually a good idea to not change the semantics of an API in a > > backward incompatible way without changing the syntax as well. > > We're taking two setattr flags ATTR_KILL_SGID, and ATTR_KILL_SUID which > have existed for several years in the VFS, and making them visible to > the filesystems. Out-of-tree filesystems that care can check for them in > a completely backward compatible way: you don't even need to add a > #define. Making flags visible is not the problem. Making another flag invisible (ATTR_MODE) at the same time _is_. > > This is true regardless of whether we care about out-of-tree code or > > not (and we should care to some degree). And especially true if the > > change in question is security sensitive. > > It is not true "regardless": the in-tree code is being converted. > Out-of-tree code is the only "problem" here, and their only problem is > that they may have to add support for the new flags if they also support > suid/sgid mode bits. Yes. And there would be no problem with that, as long as it would be breaking the API in a visible way. It does not do that and that is unsafe. The other thing with this change is, that it's generally a good idea to let the VFS do as much as possible, because then filesystem writers won't get it wrong. In this case the suid/sgid check needs to be omitted for _very_ few filesystems (NFS and fuse). So it makes sense to leave the check outside filesystem code, and move it inside only when necessary. > Are you advocating reserving a new filesystem bit every time we need to > add an attribute flag? No, just adding a flag does not constitute a backward incompatible change. Miklos - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
