linux-kernel - RE: possible deadlock in cma_netdev

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Message-Id: <OF0C6D63D8.F1817050-ON0025851B.0059D878-0025851B.0059D887@notes.na.collabserv.com>
Date:   Thu, 27 Feb 2020 16:21:21 +0000
From:   "Bernard Metzler" <BMT@...ich.ibm.com>
To:     "Jason Gunthorpe" <jgg@...pe.ca>
Cc:     "syzbot" <syzbot+55de90ab5f44172b0c90@...kaller.appspotmail.com>,
        chuck.lever@...cle.com, dledford@...hat.com, leon@...nel.org,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        netdev@...r.kernel.org, parav@...lanox.com,
        syzkaller-bugs@...glegroups.com, willy@...radead.org
Subject: RE: possible deadlock in cma_netdev_callback

-----"Jason Gunthorpe" <jgg@...pe.ca> wrote: -----

>To: "Bernard Metzler" <BMT@...ich.ibm.com>
>From: "Jason Gunthorpe" <jgg@...pe.ca>
>Date: 02/27/2020 04:53PM
>Cc: "syzbot" <syzbot+55de90ab5f44172b0c90@...kaller.appspotmail.com>,
>chuck.lever@...cle.com, dledford@...hat.com, leon@...nel.org,
>linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
>netdev@...r.kernel.org, parav@...lanox.com,
>syzkaller-bugs@...glegroups.com, willy@...radead.org
>Subject: [EXTERNAL] Re: possible deadlock in cma_netdev_callback
>
>On Thu, Feb 27, 2020 at 10:11:13AM +0000, Bernard Metzler wrote:
>
>> Thanks for letting me know! Hmm, we cannot use RCU locks since
>> we potentially sleep. One solution would be to create a list
>> of matching interfaces while under lock, unlock and use that
>> list for calling siw_listen_address() (which may sleep),
>> right...?
>
>Why do you need to iterate over addresses anyhow? Shouldn't the
>listen
>just be done with the address the user gave and a BIND DEVICE to the
>device siw is connected to?

The user may give a wildcard local address, so we'd have
to bind to all addresses of that device...

Best,
Bernard.

>
>Also that loop in siw_create looks wrong to me
>
>Jason
>
>