Re: [PATCH v2] vfs: Tighten up linkat(..., AT_EMPTY_PATH)

[Linus Torvalds]

On Sun, Aug 25, 2013 at 1:23 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> So I'll just go back to square one, and wonder if we could/should just
> make the rule be that in order to be in that LAST_BIND case, you
> really have to have f_cred match your own credentials. Or have
> CAP_SEARCH.

Nope. That doesn't work. It breaks the chrome sandboxing.

Right now, following a /proc fd symlink requires ptrace access to the
process. Which is actually pretty strict, and makes sense. But it does
mean that there are other capabilities than CAP_DAC_READ_SEARCH at
play.

I'm playing with a patch that then in addition to the ptrace check
*also* requires that the file was opened with the same credentials as
the follower _or_ the task being followed. I'll see if that works out.

                Linus
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