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Message-ID: <tencent_942CC5C35E410E3545C2E386BE566B8B1405@qq.com>
From:   Zhang Shurong <zhang_shurong@foxmail.com>
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     jgross@suse.com, xen-devel@lists.xenproject.org,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] xen: fix potential shift out-of-bounds in xenhcd_hub_control()
Date:   Sun, 06 Aug 2023 22:11:43 +0800
In-Reply-To: <4825193.GXAFRqVoOG@localhost.localdomain>
References: <tencent_15DD79B42AD8A0D64A7CDC24D4FE6C85800A@qq.com>
 <2023062628-shame-ebook-56f2@gregkh>
 <4825193.GXAFRqVoOG@localhost.localdomain>
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=E5=9C=A8 2023=E5=B9=B47=E6=9C=881=E6=97=A5=E6=98=9F=E6=9C=9F=E5=85=AD CST =
=E4=B8=8B=E5=8D=8811:51:43=EF=BC=8CZhang Shurong =E5=86=99=E9=81=93=EF=BC=9A
> =E5=9C=A8 2023=E5=B9=B46=E6=9C=8826=E6=97=A5=E6=98=9F=E6=9C=9F=E4=B8=80 C=
ST =E4=B8=8B=E5=8D=881:52:02=EF=BC=8C=E6=82=A8=E5=86=99=E9=81=93=EF=BC=9A
>=20
> > On Mon, Jun 26, 2023 at 07:48:05AM +0200, Jan Beulich wrote:
> > > On 25.06.2023 18:42, Zhang Shurong wrote:
> > > > --- a/drivers/usb/host/xen-hcd.c
> > > > +++ b/drivers/usb/host/xen-hcd.c
> > > > @@ -456,6 +456,8 @@ static int xenhcd_hub_control(struct usb_hcd *h=
cd,
> > > > __u16 typeReq, __u16 wValue,> >
> > > >=20
> > > >  			info->ports[wIndex - 1].c_connection =3D
>=20
> false;
>=20
> > > >  			fallthrough;
> > > >  	=09
> > > >  		default:
> > > > +			if (wValue >=3D 32)
> > > > +				goto error;
> > > >=20
> > > >  			info->ports[wIndex - 1].status &=3D ~(1
>=20
> << wValue);
>=20
> > > Even 31 is out of bounds (as in: UB) as long as it's 1 here rather
> > > than 1u.
> >=20
> > Why isn't the caller fixed so this type of value could never be passed
> > to the hub_control callback?
> >=20
> > thanks,
> >=20
> > greg k-h
>=20
> Although I'm not knowledgeable about the USB subsystem, I've observed that
> not all driver code that implements hub_control callback performs a shift
> operation on wValue, and not all shift operations among them cause
> problems. Therefore, I've decided to fix this issue within each driver
> itself.
>=20
> For example, in r8a66597_hub_control, it will first check whether wValue =
is
> valid (always < 31) before the shift operation. In case of an invalid
> number, the code would execute the error branch instead of the shift
> operation.
>=20
> switch (wValue) {
> case USB_PORT_FEAT_ENABLE:
> 	rh->port &=3D ~USB_PORT_STAT_POWER;
> 	break;
> case USB_PORT_FEAT_SUSPEND:
> 	break;
> case USB_PORT_FEAT_POWER:
> 	r8a66597_port_power(r8a66597, port, 0);
> 	break;
> case USB_PORT_FEAT_C_ENABLE:
> case USB_PORT_FEAT_C_SUSPEND:
> case USB_PORT_FEAT_C_CONNECTION:
> case USB_PORT_FEAT_C_OVER_CURRENT:
> case USB_PORT_FEAT_C_RESET:
> 	break;
> default:
> 	goto error;
> }
> rh->port &=3D ~(1 << wValue);

Hi there. I apologize for reaching out once more. I'm feeling a bit puzzled=
=20
about what my next step should be. I'm unsure whether I should rewrite this=
=20
patch or attempt to address the issue at the caller level.