linux-kernel - Re: [PATCH] iommu: check if group is NULL before remove device

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Message-ID: <F2ABC95E-D39F-4713-8959-91366DE4ECB8@fw-web.de>
Date:   Wed, 28 Jul 2021 12:35:07 +0200
From:   Frank Wunderlich <linux@...web.de>
To:     Joerg Roedel <joro@...tes.org>
CC:     iommu@...ts.linux-foundation.org,
        Frank Wunderlich <frank-w@...lic-files.de>,
        Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
        yong.wu@...iatek.com
Subject: Re: [PATCH] iommu: check if group is NULL before remove device

Hi Joerg,

Sorry for late reply, somehow i marked message as read without answering it.

Am 15. Juli 2021 09:20:04 MESZ schrieb Joerg Roedel <joro@...tes.org>:
>On Thu, Jul 15, 2021 at 09:11:50AM +0200, Frank Wunderlich wrote:
>> From: Frank Wunderlich <frank-w@...lic-files.de>
>> 
>> if probe is failing, iommu_group may be not initialized,
>
>Sentences start with capital letters.
>
>IOMMU patch subjects too, after the 'iommu:' prefix.

Will fix these in v2

>> so freeing it will result in NULL pointer access
>
>Please describe in more detail how this NULL-ptr dereference is
>triggered.

I had this by testing this series: 
https://patchwork.kernel.org/project/linux-mediatek/list/?series=515129

Initialization in mtk driver was failed (i guess the iommu group was not yet created), cleanup was started and so this function is called with a NULL group pointer. I can try to find my debug-trace if you need a kind of backtrace.

regards Frank