linux-kernel - Re: [PATCH v2] pid: Fix error return value in some cases

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Date:   Sat, 7 Mar 2020 07:11:36 -0600
From:   Corey Minyard <cminyard@...sta.com>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     minyard@....org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Adrian Reber <areber@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Andrei Vagin <avagin@...il.com>
Subject: Re: [PATCH v2] pid: Fix error return value in some cases

On Sat, Mar 07, 2020 at 12:00:07PM +0100, Christian Brauner wrote:
> On Fri, Mar 06, 2020 at 11:23:14AM -0600, minyard@....org wrote:
> > From: Corey Minyard <cminyard@...sta.com>
> > 
> > Recent changes to alloc_pid() allow the pid number to be specified on
> > the command line.  If set_tid_size is set, then the code scanning the
> > levels will hard-set retval to -EPERM, overriding it's previous -ENOMEM
> > value.
> > 
> > After the code scanning the levels, there are error returns that do not
> > set retval, assuming it is still set to -ENOMEM.
> > 
> > So set retval back to -ENOMEM after scanning the levels.
> > 
> > Fixes: 49cb2fc42ce4 "fork: extend clone3() to support setting a PID"
> > Signed-off-by: Corey Minyard <cminyard@...sta.com>
> > Cc: <stable@...r.kernel.org> # 5.5
> > Cc: Adrian Reber <areber@...hat.com>
> > Cc: Christian Brauner <christian.brauner@...ntu.com>
> > Cc: Oleg Nesterov <oleg@...hat.com>
> > Cc: Dmitry Safonov <0x7f454c46@...il.com>
> > Cc: Andrei Vagin <avagin@...il.com>
> 
> Thanks! I've pulled the patch now and applied.
> 
> I think that restores the old behavior. If you don't mind, I'll add a
> comment on top of it saying something like:
> "ENOMEM is not the most obvious choice but it's the what we've been
>  exposing to userspace for a long time and it's also documented
>  behavior. So we can't easily change it to something more sensible."

That's great.  I was just looking through the code for another reason
and noticed the issue.  Every little thing counts for quality.

-corey

> 
> Acked-by: Christian Brauner <christian.brauner@...ntu.com>