From:   "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To:     syzkaller-bugs@googlegroups.com
Cc:     syzbot <syzbot+355c68b459d1d96c4d06@syzkaller.appspotmail.com>,
        syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org,
        Hillf Danton <hdanton@sina.com>
Subject: Re: [syzbot] WARNING in usb_tx_block/usb_submit_urb
Date:   Thu, 16 Feb 2023 10:21:33 +0100
Message-ID: <2878263.e9J7NaK4W3@suse>
In-Reply-To: <20230216081834.1432-1-hdanton@sina.com>
References: <20230215110515.3833-1-hdanton@sina.com>
 <20230216081834.1432-1-hdanton@sina.com>
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset="iso-8859-1"
Precedence: bulk

On gioved=EC 16 febbraio 2023 09:18:34 CET Hillf Danton wrote:
> Fabio!
>=20
> On Thu, 16 Feb 2023 07:54:08 +0100 Fabio M. De Francesco
> <fmdefrancesco@gmail.com>
> > >  	do {
> > >  =09
> > >  		int j =3D3D 0;
> > >  		i++;
> > >=20
> > > -		if_usb_issue_boot_command(cardp, BOOT_CMD_FW_BY_USB);
> >=20
> > Don't we need to call if_usb_issue_boot_command() in a loop in order to
> > retry
> > the command?
>=20
> Nope certainly because of no sense made by sending it again, given no
> response this round.
>=20

Your argument looks reasonable but...

=46or what regards subsystems/drivers whose I'm not expert I always assume =
that=20
the authors know what they do despite bugs. I mean that looks more probable=
=20
that they have reasons to issue several calls to if_usb_issue_boot_command(=
) /=20
usb_submit_urb in a loop. May be that those usb_submit_urb get lost in some=
=20
particular conditions, since they decide to try if_usb_issue_boot_command()=
 in=20
a loop (but forget to kill the URB before next iteration).

I have no reasons to think you are wrong. However I don't understand the=20
reason that made you leave the loops untouched (except the line with the ca=
ll=20
to if_usb_issue_boot_command().

I suppose that, if you confirm that we have no reasons to reiterate that ca=
ll,=20
you should also leave only one loop waiting for response.

Am I missing something?

Thanks,

=46abio