linux-kernel - [PATCH 3.10 148/268] futex: Move futex_init() to core

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Date:   Mon, 19 Jun 2017 20:30:47 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Yang Yang <yang.yang29@....com.cn>, jiang.biao2@....com.cn,
        jiang.zhengxiong@....com.cn, zhong.weidong@....com.cn,
        deng.huali@....com.cn, Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 148/268] futex: Move futex_init() to core_initcall

From: Yang Yang <yang.yang29@....com.cn>

commit 25f71d1c3e98ef0e52371746220d66458eac75bc upstream.

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@....com.cn>
Cc: jiang.biao2@....com.cn
Cc: jiang.zhengxiong@....com.cn
Cc: zhong.weidong@....com.cn
Cc: deng.huali@....com.cn
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/1483085875-6130-1-git-send-email-yang.yang29@zte.com.cn
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Willy Tarreau <w@....eu>
---
 kernel/futex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index edc4bea..9bbeda0 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2902,4 +2902,4 @@ static int __init futex_init(void)

 	return 0;
 }
-__initcall(futex_init);
+core_initcall(futex_init);
-- 
2.8.0.rc2.1.gbe9624a