Re: [1/1][PATCH] nproc v2: netlink access to /proc information

Roger Luethi
2004-09-14T18:59:11Z

On Tue, 14 Sep 2004 11:37:36 -0700, Chris Wright wrote:
> * William Lee Irwin III (wli@holomorphy.com) wrote:
> > On Tue, 14 Sep 2004 08:37:58 -0700, William Lee Irwin III wrote:
> > >> No, in general races of the form "permissions were altered after I
> > >> checked them" can happen.
> >
> > On Tue, Sep 14, 2004 at 06:01:50PM +0200, Roger Luethi wrote:
> > > Can you make an example? Some scenario where this would be important?
> >
> > Not particularly. It largely means poorly-coded apps may report gibberish.
>
> Canonical example is access(2) followed by open(2), not really relevant
> in this case. However, exec setuid root app...when do you check, and
> when to you fill in data to send back to user? For /proc, this type of
> check happens often (see things like may_ptrace_attach and
> task_dumpable in fs/proc/base.c).

For nproc, the procedure looks like this: A tool send(2)s a request,
credentials are attached to skb. Based on said credentials, the kernel
is free to provide (netlink_unicast to originating socket) or withhold
information. In this regard, nproc works like other netlink interfaces.

Roger