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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Kees Cook <keescook@chromium.org>,
	David Laight <David.Laight@aculab.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"mingo@kernel.org" <mingo@kernel.org>,
	"jiangshanlai@gmail.com" <jiangshanlai@gmail.com>,
	"dipankar@in.ibm.com" <dipankar@in.ibm.com>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"mathieu.desnoyers@efficios.com" <mathieu.desnoyers@efficios.com>,
	"josh@joshtriplett.org" <josh@joshtriplett.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"rostedt@goodmis.org" <rostedt@goodmis.org>,
	"dhowells@redhat.com" <dhowells@redhat.com>,
	"edumazet@google.com" <edumazet@google.com>,
	"fweisbec@gmail.com" <fweisbec@gmail.com>,
	"oleg@redhat.com" <oleg@redhat.com>
Subject: Re: [PATCH tip/core/rcu 02/20] torture: Prepare scripting for shift from %p to %pK
Date: Sun, 10 Dec 2017 12:39:11 -0800
Message-ID: <CA+55aFwQEd_d40g4mUCSsVRZzrFPUJt74vc6PPpb675hYNXcKw@mail.gmail.com> (raw)
In-Reply-To: <CAHp75VcJKYnW2grD6jViNFU3z6+fJoTmqs+ZP3Xm6YB3C8ZH1Q@mail.gmail.com>

On Sun, Dec 10, 2017 at 4:52 AM, Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
>>
>>> Perhaps it should have printed a fixed, non-zero value for non-zero
>>> pointers.
>>
>> I must leave this to the people who have a dog in that contest.  ;-)
>
> Since there is an ongoing discussion with security people near to %pK
> and alike, I added Kees and Linus to Cc list.
>
> The proposed change can be done easily, though I have no knowledge
> about possible implications.

I'd rather make %pK act more like %p than have gratuitous differences.

I also think %pK is kind of pointless in general. It has not been a
big success, and the whole "root or not" is kind of nasty anyway. Root
in a container? Things like that.

So I think that if people worry  about leaking pointers, they should
primarily go for:

 - just use %p and now get the hashed value

 - if the hashed value is pointless, ask yourself whether the pointer
itself is important. Maybe it should be removed?

 - as a last option, if you really  think the true pointer value is
important, why is root so special, and maybe you should use %px and
make sure you have proper sensible permissions.

..and %pK just isn't really the answer in any of those cases.

         Linus

  parent reply index

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-01 20:08 [PATCH tip/core/rcu 0/20] Torture-test updates for v4.16 Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 01/20] torture: Suppress CPU stall warnings during shutdown ftrace dump Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 02/20] torture: Prepare scripting for shift from %p to %pK Paul E. McKenney
2017-12-04 12:32   ` David Laight
2017-12-04 13:42     ` Paul E. McKenney
2017-12-04 14:13       ` David Laight
2017-12-04 16:11         ` Paul E. McKenney
2017-12-10 12:52           ` Andy Shevchenko
2017-12-10 18:51             ` Paul E. McKenney
2017-12-10 20:39             ` Linus Torvalds [this message]
2017-12-10 21:47               ` Paul E. McKenney
2017-12-11 19:59                 ` Kees Cook
2017-12-12 16:08                   ` Paul E. McKenney
     [not found]               ` <87wp1sa55h.fsf@concordia.ellerman.id.au>
     [not found]                 ` <CA+55aFxHdAX_ztDMUyXihhUv_eftntHecGUUaV3qAtGj_ZbKCg@mail.gmail.com>
2017-12-13 12:59                   ` Long live %pK (was Re: [PATCH tip/core/rcu 02/20] torture: Prepare scripting for shift from %p to %pK) Michael Ellerman
2017-12-13 18:21                     ` Linus Torvalds
2017-12-01 20:08 ` [PATCH tip/core/rcu 03/20] rcutorture: Change printk() %p to %pK Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 04/20] torture: Reduce #ifdefs for preempt_schedule() Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 05/20] rcutorture: Preempt RCU-preempt readers more vigorously Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 06/20] rcutorture/configinit: Fix build directory error message Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 07/20] rcutorture: Remove unused script, config2frag.sh Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 08/20] rcutorture/kvm.sh: Remove unused variable, `alldone` Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 09/20] rcutorture/kvm.sh: Use consistent help text for --qemu-args Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 10/20] rcutorture/kvm.sh: Support execution from any directory Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 11/20] rcutorture/kvm-recheck-*: Improve result directory readability check Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 12/20] rcutorture: Simplify logging Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 13/20] rcutorture: Simplify functions.sh include path Paul E. McKenney
2017-12-01 20:08 ` [PATCH tip/core/rcu 14/20] rcutorture/kvm-build.sh: Skip build directory check Paul E. McKenney
2017-12-01 20:09 ` [PATCH tip/core/rcu 15/20] torture: Place all torture-test modules in one MAINTAINERS group Paul E. McKenney
2017-12-01 20:09 ` [PATCH tip/core/rcu 16/20] locking/locktorture: Fix rwsem reader_delay Paul E. McKenney
2017-12-01 20:09 ` [PATCH tip/core/rcu 17/20] locking/locktorture: Fix num reader/writer corner cases Paul E. McKenney
2017-12-01 20:09 ` [PATCH tip/core/rcu 18/20] torture: Make stutter less vulnerable to compilers and races Paul E. McKenney
2017-12-01 20:09 ` [PATCH tip/core/rcu 19/20] torture: Eliminate torture_runnable and perf_runnable Paul E. McKenney
2017-12-01 20:09 ` [PATCH tip/core/rcu 20/20] torture: Save a line in stutter_wait(): while -> for Paul E. McKenney

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