Re: [PATCH] utime(s): Honour CAP_FOWNER when times==NULL

[Al Viro <viro@ftp.linux.org.uk>]

On Tue, Jul 17, 2007 at 01:00:42AM +0530, Satyam Sharma wrote:
> > 	if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
> > 
> > test is a rather common test, and in fact, arguably, every time you see 
> > one part of it, you should probably see the other. Would it make sense to 
> > make a helper inline function to do this, and replace all users? Doing a
> > 
> > 	git grep 'fsuid.*\<i_uid\>'
> > 
> > seems to show quite a few cases of this pattern..
> 
> Yes, I thought of writing a helper function for this myself. The semantics
> of CAP_FOWNER sort of justify that, but probably better to get Al's views
> on this first.

Helper makes sense (and most of these places will become its call), but...
E.g. IIRC the change of UID requires CAP_CHOWN; CAP_FOWNER is not enough.
Ditto for change of GID.  setlease() is using CAP_LEASE and that appears
to be intentional (no idea what relevant standards say here)...

I'd suggest converting the obvious cases with new helper and taking the
rest one-by-one after that.  Some of those might want CAP_FOWNER added,
some not...