linux-kernel - Re: [PATCH v3] scripts: add leaking

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Message-ID: <20171107174413.00e51a3f@gandalf.local.home>
Date:   Tue, 7 Nov 2017 17:44:13 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        "Tobin C. Harding" <me@...in.cc>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Andy Lutomirski <luto@...nel.org>,
        Joe Perches <joe@...ches.com>,
        Network Development <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        "Theodore Ts'o" <tytso@....edu>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Tycho Andersen <tycho@...ker.com>,
        "Roberts, William C" <william.c.roberts@...el.com>,
        Tejun Heo <tj@...nel.org>,
        Jordan Glover <Golden_Miller83@...tonmail.ch>,
        Greg KH <gregkh@...uxfoundation.org>,
        Petr Mladek <pmladek@...e.com>,
        Ian Campbell <ijc@...lion.org.uk>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <wilal.deacon@....com>,
        Chris Fries <cfries@...gle.com>,
        Dave Weinstein <olorin@...gle.com>,
        Daniel Micay <danielmicay@...il.com>,
        Djalal Harouni <tixxdz@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3] scripts: add leaking_addresses.pl

On Tue, 7 Nov 2017 13:44:01 -0800
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> > Looking other places that stand out, it seems like
> > /proc/lockdep_chains and /proc/lockdep (CONFIG_LOCKDEP=y) has a ton of
> > %p usage. It's unclear to me if a hash is sufficient for meaningful
> > debugging there?  
> 
> Maybe not, but that is also _so_ esoteric that I suspect the right fix
> is to just make it root-only readable.

Also note, I don't believe anyone should be running a LOCKDEP
configured kernel in a production (secured) environment. As it adds
quite a bit of overhead. It's something you run on test environments to
make sure it doesn't detect any possible deadlocks.

> 
> I've never used it, we should check with people who have. I get the
> feeling that this is purely for PeterZ debugging.

I've used it. But then again, I also debug lockdep ;-)

> 
> The very first commit that introduced that code actually has a
> 
>     (FIXME: should go into debugfs)
> 
> so I suspect it never should have been user-readable to begin with. I
> guess it makes some things easier, but it really is *very* different
> from things like profiling.

Want me to whip up a patch to move the file?

-- Steve

> 
> Profiling you often *cannot* do as root - some things you profile
> really shouldn't be run as root, and might even refuse to do so. So
> requiring you to be root just to get a kernel profile is very bad.
> 
> But looking at lockdep stats? Yeah, 'sudo' isn't so big of a deal.
> 
>