futex: Mark get_robust_list as deprecated

Notify get_robust_list users that the syscall is going away.

Suggested-by: Thomas Gleixner <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Darren Hart <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Jiri Kosina <[email protected]>
Cc: Eric W. Biederman <[email protected]>
Cc: David Howells <[email protected]>
Cc: Serge E. Hallyn <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

Documentation/feature-removal-schedule.txt

@@ -529,3 +529,13 @@ 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 <[email protected]>
+
+----------------------------
+
+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 <[email protected]>

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;

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;