[tip:locking/urgent] futex: Move futex_init() to core_initcall

[tip-bot for Yang Yang]

Commit-ID:  25f71d1c3e98ef0e52371746220d66458eac75bc
Gitweb:     http://git.kernel.org/tip/25f71d1c3e98ef0e52371746220d66458eac75bc
Author:     Yang Yang <yang.yang29@xxxxxxxxxx>
AuthorDate: Fri, 30 Dec 2016 16:17:55 +0800
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Mon, 13 Feb 2017 16:12:22 +0100

futex: Move futex_init() to core_initcall

The UEVENT user mode helper is enabled before the initcalls are executed
and is available when the root filesystem has been mounted.

The user mode helper is triggered by device init calls and the executable
might use the futex syscall.

futex_init() is marked __initcall which maps to device_initcall, but there
is no guarantee that futex_init() is invoked _before_ the first device init
call which triggers the UEVENT user mode helper.

If the user mode helper uses the futex syscall before futex_init() then the
syscall crashes with a NULL pointer dereference because the futex subsystem
has not been initialized yet.

Move futex_init() to core_initcall so futexes are initialized before the
root filesystem is mounted and the usermode helper becomes available.

[ tglx: Rewrote changelog ]

Signed-off-by: Yang Yang <yang.yang29@xxxxxxxxxx>
Cc: jiang.biao2@xxxxxxxxxx
Cc: jiang.zhengxiong@xxxxxxxxxx
Cc: zhong.weidong@xxxxxxxxxx
Cc: deng.huali@xxxxxxxxxx
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1483085875-6130-1-git-send-email-yang.yang29@xxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 kernel/futex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 0842c8ca..cdf3650 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3323,4 +3323,4 @@ static int __init futex_init(void)
 
 	return 0;
 }
-__initcall(futex_init);
+core_initcall(futex_init);