Re: [PATCH] futex: do not leak robust list to unprivileged process
From: Thomas Gleixner
Date: Wed Mar 28 2012 - 17:24:17 EST
On Wed, 28 Mar 2012, Kees Cook wrote:
> On Thu, Mar 22, 2012 at 4:46 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> > On Tue, 20 Mar 2012, Ingo Molnar wrote:
> >> * Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> >> > On Tue, Mar 20, 2012 at 10:02 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> >> > > I really wonder why we have this syscall at all.
> >> >
> >> > The documentation I found yesterday while looking at this was:
> >> > http://linux.die.net/man/2/get_robust_list
> >> >
> >> > Which says "The system call is only available for debugging
> >> > purposes and is not needed for normal operations. Both system
> >> > calls are not available to application programs as functions;
> >> > they can be called using the syscall(3) function."
> >> >
> >> > Dropping the syscall entirely would certainly make it secure.
> >> > ;)
> >> The thinking was API completeness. In general it's possible for
> >> a sufficiently privileged task to figure out all the state of a
> >> task. We can query timers, fds - the robust list is such a
> >> resource as well. The information leakage was obviously not
> >> intended.
> > So I think it's safe to take Kees' patch as is. On top of that we
> > should add a WARN_ONCE when the syscall is invoked and schedule the
> > sucker for removal.
> Can someone claim the first patch? It looks like not everyone agrees
> about removal, but I'd like to see at least the first one get in. :)
It's on my list for tomorrow.
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