Re: [PATCH 4.9.257 1/1] futex: Fix OWNER_DEAD fixup

[Greg KH]

On Mon, Feb 22, 2021 at 08:20:38PM +0800, Zhengyejian (Zetta) wrote:
> 
> 
> On 2021/2/22 20:07, Greg KH wrote:
> > 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@xxxxxxxxxxxxx>
> > > > 
> > > > 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@xxxxxxxxxxxxxx>
> > > > Reported-by: Dave Jones <davej@xxxxxxxxxxxxxxxxx>
> > > > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> > > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > > > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > > > Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
> > > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > > > Fixes: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")
> > > > Link: http://lkml.kernel.org/r/20180122103947.GD2228@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> > > > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> > > > Signed-off-by: Zheng Yejian <zhengyejian1@xxxxxxxxxx>
> > > > ---
> > > >   kernel/futex.c | 7 +++----
> > > >   1 file changed, 3 insertions(+), 4 deletions(-)
> > > 
> > > Reviewed-by: Lee Jones <lee.jones@xxxxxxxxxx>
> > 
> > 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
> > .
> > 
> I make the patch basing on 282aeb477a10 ("Linux 4.9.257").
> Should I base on f0cf73f13b39 ("Linux 4.9.258-rc1")?

Yes please as I think this is already there.

How about just waiting for the next release to come out, I will push out
the 4.4 and 4.9 -rc releases right now as well to give everyone a chance
to sync up properly.

thanks,

greg k-h