Re: Linux 3.6

[Kees Cook <kees@outflux.net>]

On Thu, Oct 04, 2012 at 09:35:04AM -0400, Nick Bowler wrote:
> On 2012-10-03 13:54 -0700, Linus Torvalds wrote:
> > On Wed, Oct 3, 2012 at 1:49 PM, Kees Cook <kees@outflux.net> wrote:
> > > I think the benefits of this being on by default outweigh glitches
> > > like this. Based on Nick's email, it looks like a directory tree of his
> > > own creation.
> > 
> > I agree that *one* report like this doesn't necessarily mean that we
> > need to turn it off, if Nick is happy to just fix up his script and
> > it's all local.
> > 
> > However, I suspect we'll see more. And once that happens, we're not
> > going to keep a default that breaks peoples old scripts, and we're
> > going to have to rely on distributions (or users) explicitly setting
> > it.
> 
> Yes, it is a directory of my own creation, intended as a place for users
> (read: me) to stick stuff on the local disk as opposed to on NFS.  It's
> pretty trivial for me to fixup everything to not need this symlink
> anymore (and I suspect it is the only offender); I just created the
> symlink in the first place so that I wouldn't have to change anything
> else.
> 
> (While on /this/ machine I created the directory, I have used shared lab
> machines with a similar setup).
> 
> The thing that bothers me most about all this is that it's basically
> impossible to see why things are failing without digging through the git
> tree or posting to the mailing list (or recalling earlier mailing list
> discussions about the restriction, as I vaguely do now).  You just
> suddenly get "permission denied" errors when all the permissions
> involved look fine.  As far as I know, the owner, group and mode of
> symlinks have always been completely meaningless.  Upgrade to 3.6, and
> they're suddenly meaningful in extremely non-obvious ways.

FWIW, there should have been an audit message about it in dmesg.

-Kees

-- 
Kees Cook                                            @outflux.net