sysctl: make CONFIG_SYSCTL_SYSCALL default to n

When I tried to send a patch to remove it, Andi told me we still need to
keep compabitlies for old libc, so we can't remove this completely.  Then
just make it default to n and remove the doc from
feature-removal-schedule.txt.

Signed-off-by: WANG Cong <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Documentation/feature-removal-schedule.txt

@@ -133,41 +133,6 @@ Who:	Pavel Machek <[email protected]>
 
 ---------------------------
 
-What:	sys_sysctl
-When:	September 2010
-Option: CONFIG_SYSCTL_SYSCALL
-Why:	The same information is available in a more convenient from
-	/proc/sys, and none of the sysctl variables appear to be
-	important performance wise.
-
-	Binary sysctls are a long standing source of subtle kernel
-	bugs and security issues.
-
-	When I looked several months ago all I could find after
-	searching several distributions were 5 user space programs and
-	glibc (which falls back to /proc/sys) using this syscall.
-
-	The man page for sysctl(2) documents it as unusable for user
-	space programs.
-
-	sysctl(2) is not generally ABI compatible to a 32bit user
-	space application on a 64bit and a 32bit kernel.
-
-	For the last several months the policy has been no new binary
-	sysctls and no one has put forward an argument to use them.
-
-	Binary sysctls issues seem to keep happening appearing so
-	properly deprecating them (with a warning to user space) and a
-	2 year grace warning period will mean eventually we can kill
-	them and end the pain.
-
-	In the mean time individual binary sysctls can be dealt with
-	in a piecewise fashion.
-
-Who:	Eric Biederman <[email protected]>
-
----------------------------
-
 What:	/proc/<pid>/oom_adj
 When:	August 2012
 Why:	/proc/<pid>/oom_adj allows userspace to influence the oom killer's

init/Kconfig

@@ -947,7 +947,7 @@ config UID16
 config SYSCTL_SYSCALL
 	bool "Sysctl syscall support" if EXPERT
 	depends on PROC_SYSCTL
-	default y
+	default n
 	select SYSCTL
 	---help---
 	  sys_sysctl uses binary paths that have been found challenging
@@ -959,7 +959,7 @@ config SYSCTL_SYSCALL
 	  trying to save some space it is probably safe to disable this,
 	  making your kernel marginally smaller.
 
-	  If unsure say Y here.
+	  If unsure say N here.
 
 config KALLSYMS
 	 bool "Load all symbols for debugging/ksymoops" if EXPERT