linux-kernel - Re: [PATCH 4.9.258] futex: fix dead code in attach_to_pi

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Date:   Mon, 1 Mar 2021 15:19:11 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Xiaoming Ni <nixiaoming@...wei.com>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, sashal@...nel.org, tglx@...utronix.de,
        wangle6@...wei.com, zhengyejian1@...wei.com
Subject: Re: [PATCH 4.9.258] futex: fix dead code in attach_to_pi_owner()

On Thu, Feb 25, 2021 at 09:17:38AM +0000, Lee Jones wrote:
> On Wed, 24 Feb 2021, Xiaoming Ni wrote:
> 
> > The handle_exit_race() function is defined in commit 9c3f39860367
> >  ("futex: Cure exit race"), which never returns -EBUSY. This results
> > in a small piece of dead code in the attach_to_pi_owner() function:
> > 
> > 	int ret = handle_exit_race(uaddr, uval, p); /* Never return -EBUSY */
> > 	...
> > 	if (ret == -EBUSY)
> > 		*exiting = p; /* dead code */
> > 
> > The return value -EBUSY is added to handle_exit_race() in upsteam
> > commit ac31c7ff8624409 ("futex: Provide distinct return value when
> > owner is exiting"). This commit was incorporated into v4.9.255, before
> > the function handle_exit_race() was introduced, whitout Modify
> > handle_exit_race().
> > 
> > To fix dead code, extract the change of handle_exit_race() from
> > commit ac31c7ff8624409 ("futex: Provide distinct return value when owner
> >  is exiting"), re-incorporated.
> > 
> > Fixes: 9c3f39860367 ("futex: Cure exit race")
> > Cc: stable@...r.kernel.org # v4.9.258
> > Signed-off-by: Xiaoming Ni <nixiaoming@...wei.com>
> > ---
> >  kernel/futex.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> To clarify, this is not a wholesale back-port from Mainline.
> 
> It takes the remaining functional snippet of:
> 
>  ac31c7ff8624409 ("futex: Provide distinct return value when owner is exiting")
> 
> ... and is the correct fix for this issue.
> 
> Reviewed-by: Lee Jones <lee.jones@...aro.org>

Thanks, now queued up.

greg k-h