From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>
Subject: Re: [bug report] iommu/arm-smmu: Make use of the iommu_register
	interface
Date: Wed, 22 Feb 2017 12:00:42 +0100
Message-ID: <20170222110042.GC4154@suse.de>
References: <20170215083648.GA12604@mwanda>
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To: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
Cc: will.deacon-5wv7dgnIgG8@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
List-Id: iommu@lists.linux-foundation.org

Hi Dan,

thanks for the report! There are more bogus things going on here.

On Wed, Feb 15, 2017 at 11:36:48AM +0300, Dan Carpenter wrote:
> The patch 9648cbc9625b: "iommu/arm-smmu: Make use of the 
> iommu_register interface" from Feb 1, 2017, leads to the following 
> Smatch complaint:
> 
> drivers/iommu/arm-smmu-v3.c:1810 arm_smmu_remove_device()
> 	 warn: variable dereferenced before check 'master' (see line 1809)
> 
> drivers/iommu/arm-smmu-v3.c
>   1808		master = fwspec->iommu_priv;
>   1809		smmu = master->smmu;
>                        ^^^^^^^^^^^^
> New dereference.
> 
>   1810		if (master && master->ste.valid)
>                     ^^^^^^
> Old code checked for NULL.
> 
>   1811			arm_smmu_detach_dev(dev);
>   1812		iommu_group_remove_device(dev);

So the master pointer comes from fwspec->iommu_priv, and master is freed
later in the function. But I can't find where the fwspec->iommu_priv
pointer is cleared. To me it looks like this breaks when a device is
removed and the added again.

Robin, Will, can you have a look please?


Thanks,

	Joerg