linux-kernel - Re: [PATCH v2] futex: mark get_robust

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Message-ID: <m1fwczvuph.fsf@fess.ebiederm.org>
Date:	Fri, 23 Mar 2012 15:06:02 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Kees Cook <keescook@...omium.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	Randy Dunlap <rdunlap@...otime.net>,
	Darren Hart <dvhart@...ux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>,
	David Howells <dhowells@...hat.com>,
	"Serge E. Hallyn" <serge.hallyn@...onical.com>,
	linux-doc@...r.kernel.org, kernel-hardening@...ts.openwall.com,
	spender@...ecurity.net,
	Linux Containers <containers@...ts.linux-foundation.org>
Subject: Re: [PATCH v2] futex: mark get_robust_list as deprecated

Kees Cook <keescook@...omium.org> writes:

> Notify get_robust_list users that the syscall is going away.

Has anyone asked the question if the folks working on checkpoint/restart
are going to need this.

This seems like important information to know if you want to checkpoint
a process.

Eric

> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> v2:
>  - add note to feature-removal-schedule.txt.
> ---
>  Documentation/feature-removal-schedule.txt |   10 ++++++++++
>  kernel/futex.c                             |    2 ++
>  kernel/futex_compat.c                      |    2 ++
>  3 files changed, 14 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
> index 4bfd982..e3bf119 100644
> --- a/Documentation/feature-removal-schedule.txt
> +++ b/Documentation/feature-removal-schedule.txt
> @@ -543,3 +543,13 @@ When:	3.5
>  Why:	The old kmap_atomic() with two arguments is deprecated, we only
>  	keep it for backward compatibility for few cycles and then drop it.
>  Who:	Cong Wang <amwang@...hat.com>
> +
> +----------------------------
> +
> +What:	get_robust_list syscall
> +When:	2013
> +Why:	There appear to be no production users of the get_robust_list syscall,
> +	and it runs the risk of leaking address locations, allowing the bypass
> +	of ASLR. It was only ever intended for debugging, so it should be
> +	removed.
> +Who:	Kees Cook <keescook@...omium.org>
> diff --git a/kernel/futex.c b/kernel/futex.c
> index d701be5..e2b0fb9 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -2449,6 +2449,8 @@ SYSCALL_DEFINE3(get_robust_list, int, pid,
>  	if (!futex_cmpxchg_enabled)
>  		return -ENOSYS;
>  
> +	WARN_ONCE(1, "deprecated: get_robust_list will be deleted in 2013.\n");
> +
>  	rcu_read_lock();
>  
>  	ret = -ESRCH;
> diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
> index a9642d5..83e368b 100644
> --- a/kernel/futex_compat.c
> +++ b/kernel/futex_compat.c
> @@ -142,6 +142,8 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
>  	if (!futex_cmpxchg_enabled)
>  		return -ENOSYS;
>  
> +	WARN_ONCE(1, "deprecated: get_robust_list will be deleted in 2013.\n");
> +
>  	rcu_read_lock();
>  
>  	ret = -ESRCH;
--
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