netdev - Re: [PATCH 3/3] nfc: trf7970a: Prevent repeated polling from crashing the kernel

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Message-ID: <20161220185905.GA5867@animalcreek.com>
Date:   Tue, 20 Dec 2016 11:59:05 -0700
From:   Mark Greer <mgreer@...malcreek.com>
To:     Geoff Lansberry <geoff@...ee.com>
Cc:     linux-wireless@...r.kernel.org, lauro.venancio@...nbossa.org,
        aloisio.almeida@...nbossa.org, sameo@...ux.intel.com,
        robh+dt@...nel.org, mark.rutland@....com, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        justin@...ee.com, Jaret Cantu <jaret.cantu@...esys.com>
Subject: Re: [PATCH 3/3] nfc: trf7970a: Prevent repeated polling from
 crashing the kernel

On Tue, Dec 20, 2016 at 11:16:32AM -0500, Geoff Lansberry wrote:
> From: Jaret Cantu <jaret.cantu@...esys.com>
> 
> Repeated polling attempts cause a NULL dereference error to occur.
> This is because the state of the trf7970a is currently reading but
> another request has been made to send a command before it has finished.

How is this happening?  Was trf7970a_abort_cmd() called and it didn't
work right?  Was it not called at all and there is a bug in the digital
layer?  More details please.

> The solution is to properly kill the waiting reading (workqueue)
> before failing on the send.

If the bug is in the calling code, then that is what should get fixed.
This seems to be a hack to work-around a digital layer bug.

Mark
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