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

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Message-ID: <2e079a86-9582-b4fd-5e6a-7582e95ce583@canonical.com>
Date:   Wed, 2 May 2018 09:46:00 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: re: media: rcar-vin: add group allocator functions

Hi there,

Static analysis with CoverityScan picked up an explicit null pointer
dereference in the the following commit:

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

in:

+static void rvin_group_put(struct rvin_dev *vin)
+{
+       mutex_lock(&vin->group->lock);
+
+       vin->group = NULL;

vin->group is now NULL


+       vin->v4l2_dev.mdev = NULL;
+
+       if (WARN_ON(vin->group->vin[vin->id] != vin))
+               goto out;

vin->group is being dereferenced (null pointer dereference)

+
+       vin->group->vin[vin->id] = NULL;

vin->group is being dereferenced (null pointer dereference)

+out:
+       mutex_unlock(&vin->group->lock);
+
+       kref_put(&vin->group->refcount, rvin_group_release);
+}

So I think this needs fixing up.

Regards,

Colin