linux-kernel - Re: media: rcar-vin: add group allocator functions

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Message-ID: <20180424223554.GE27674@bigcity.dyn.berto.se>
Date:   Wed, 25 Apr 2018 00:35:54 +0200
From:   "Niklas Söderlund" <niklas.soderlund@...natech.se>
To:     Colin Ian King <colin.king@...onical.com>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: media: rcar-vin: add group allocator functions

Hi Colin,

Thanks for reporting this. I wonder why smatch and sparse did not catch 
this, the fault can't be mine for writing such a obviously bad thing 
right :-)

I have a patch to address this, just need to test it before posting.

On 2018-04-24 14:14:02 +0100, Colin Ian King wrote:
> Hi there,
> 
> While running static analysis on linux-next today a null pointer
> dereference issue was detected by CoverityScan. The following commit
> introduced the issue:
> 
> commit 3bb4c3bc85bf77a76c921671800bde2e1bf82a88
> Author: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
> Date:   Sat Apr 14 07:57:18 2018 -0400
> 
>     media: rcar-vin: add group allocator functions
> 
> The analysis is as follows:
> 
> 339 static void rvin_group_put(struct rvin_dev *vin)
> 340 {
> 341        mutex_lock(&vin->group->lock);
> 342
>    1. assign_zero: Assigning: vin->group = NULL.
> 
> 343        vin->group = NULL;
> 344        vin->v4l2_dev.mdev = NULL;
> 345
>     CID 1468359 (#1 of 1): Explicit null dereferenced (FORWARD_NULL)
>     2. var_deref_op: Dereferencing null pointer vin->group.
> 
> 346        if (WARN_ON(vin->group->vin[vin->id] != vin))
> 347                goto out;
> 348
> 
> vin->group is NULL however the WARN_ON is dereferencing it, causing an
> OOPS.  I don't know how this should be fixed, hence I am sending this
> bug report.
> 
> Regards,
> 
> Colin

-- 
Regards,
Niklas Söderlund