linux-kernel - Re: [PATCH] infiniband: fix a subtle race condition

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Message-ID: <CAM_iQpWz9b01ksW_OUHgr1=pf-bNsq_TxoNCQxuDdhUXfvoyOQ@mail.gmail.com>
Date:   Thu, 14 Jun 2018 10:03:09 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Jason Gunthorpe <jgg@...lanox.com>
Cc:     Leon Romanovsky <leon@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-rdma@...r.kernel.org,
        Doug Ledford <dledford@...hat.com>
Subject: Re: [PATCH] infiniband: fix a subtle race condition

On Thu, Jun 14, 2018 at 7:24 AM, Jason Gunthorpe <jgg@...lanox.com> wrote:
>
> This was my brief reaction too, this code path almost certainly has a
> use-after-free, and we should fix the concurrency between the two
> places in some correct way..

First of all, why use-after-free could trigger an imbalance unlock?
IOW, why do we have to solve use-after-free to fix this imbalance
unlock?

Second of all, my patch is _not_ intended to solve any use-after-free,
it only solves the imbalance unlock. I never claim it solves more
anywhere.

Third of all, the use-after-free I can see (race with ->close) exists
before my patch, this patch doesn't make it better or worse, nor
I have any intend to fix it.