linux-kernel - Re: [PATCH 4.9.257 1/1] futex: Fix OWNER

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Message-ID: <YDOec1kosGKKO80g@kroah.com>
Date:   Mon, 22 Feb 2021 13:07:15 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Zheng Yejian <zhengyejian1@...wei.com>, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org, judy.chenhui@...wei.com,
        zhangjinhao2@...wei.com, tglx@...utronix.de
Subject: Re: [PATCH 4.9.257 1/1] futex: Fix OWNER_DEAD fixup

On Mon, Feb 22, 2021 at 11:54:24AM +0000, Lee Jones wrote:
> On Mon, 22 Feb 2021, Zheng Yejian wrote:
> 
> > From: Peter Zijlstra <peterz@...radead.org>
> > 
> > commit a97cb0e7b3f4c6297fd857055ae8e895f402f501 upstream.
> > 
> > Both Geert and DaveJ reported that the recent futex commit:
> > 
> >   c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")
> > 
> > introduced a problem with setting OWNER_DEAD. We set the bit on an
> > uninitialized variable and then entirely optimize it away as a
> > dead-store.
> > 
> > Move the setting of the bit to where it is more useful.
> > 
> > Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> > Reported-by: Dave Jones <davej@...emonkey.org.uk>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > Cc: Paul E. McKenney <paulmck@...ibm.com>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Fixes: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")
> > Link: http://lkml.kernel.org/r/20180122103947.GD2228@hirez.programming.kicks-ass.net
> > Signed-off-by: Ingo Molnar <mingo@...nel.org>
> > Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>
> > ---
> >  kernel/futex.c | 7 +++----
> >  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> Reviewed-by: Lee Jones <lee.jones@...aro.org>

This does not apply to the 4.9.y tree at all right now, are you all sure
you got the backport correct?

confused,

greg k-h