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

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Message-ID: <20120323190855.GA27213@www.outflux.net>
Date:	Fri, 23 Mar 2012 12:08:55 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	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>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	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
Subject: [PATCH v2] futex: mark get_robust_list as deprecated

Notify get_robust_list users that the syscall is going away.

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;
-- 
1.7.0.4

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