linux-kernel - Re: [PATCH] futex: Fix futex lock the wrong page

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Date:   Wed, 12 Jun 2019 09:15:34 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     "zhangxiaoxu (A)" <zhangxiaoxu5@...wei.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, peterz@...radead.org,
        dvhart@...radead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] futex: Fix futex lock the wrong page

On Wed, Jun 12, 2019 at 09:50:25AM +0800, zhangxiaoxu (A) wrote:
> This patch is for stable branch linux-4.4-y.
> 
> On 2019/6/12 9:54, ZhangXiaoxu wrote:
> > The upstram commit 65d8fc777f6d ("futex: Remove requirement
> > for lock_page() in get_futex_key()") use variable 'page' as
> > the page head, when merge it to stable branch, the variable
> > `page_head` is page head.
> > 
> > In the stable branch, the variable `page` not means the page
> > head, when lock the page head, we should lock 'page_head',
> > rather than 'page'.
> > 
> > It maybe lead a hung task problem.
> > 
> > Signed-off-by: ZhangXiaoxu <zhangxiaoxu5@...wei.com>
> > Cc: stable@...r.kernel.org
> > ---
> >   kernel/futex.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)

I do not understand.

Please read
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to submit a patch to the stable trees properly.

If the commit is not in Linus's tree, then we can not take it, unless
something is _very_ broken and it is the only way it can be resolved.

thanks,

greg k-h