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Date: Mon, 31 Jul 2017 17:13:00 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH for-2.10] block/qapi: Remove redundat NULL
 check to silence Coverity
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To: Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= <f4bug@amsat.org>
Cc: Jeff Cody <jcody@redhat.com>, peter.maydell@linaro.org, qemu-devel@nongnu.org, qemu-block@nongnu.org

Am 31.07.2017 um 16:54 hat Philippe Mathieu-Daud=E9 geschrieben:
> On 07/31/2017 11:38 AM, Jeff Cody wrote:
> > On Mon, Jul 31, 2017 at 02:51:11PM +0200, Kevin Wolf wrote:
> > > When skipping implicit nodes in bdrv_block_device_info(), we know t=
hat
> > > bs0 is always non-NULL; initially, because it's taken from a BdrvCh=
ild
> >=20
> > Not to mention, we deference bs0 in the chunk of code right above thi=
s, so
> > we'd segfault anyway if the initial value was NULL.

Not really. The last use of bs0 before the loop is:

    bs0 =3D bs0->backing->bs;bs0 =3D bs0->backing->bs;

So we're pointing to a different BDS now.

> Yes, please move your assert before:
>=20
> 137:    if (bs0->drv && bs0->backing) {

That would assert something completely different and much more obvious.
(And apart from that, bdrv_query_image_info() in line 130 already
dereferences bs0, so it would be too late, too.)

What I want to assert here is that every implicit image has a backing
file.

Kevin