From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from perceval.ideasonboard.com ([213.167.242.64]:52160 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727669AbeHGLLh (ORCPT ); Tue, 7 Aug 2018 07:11:37 -0400 From: Laurent Pinchart To: Nadav Amit Cc: Mauro Carvalho Chehab , "linux-media@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] usb: fix uvc_alloc_entity() allocation alignment Date: Tue, 07 Aug 2018 11:59:01 +0300 Message-ID: <3561796.imRZE4xQI7@avalon> In-Reply-To: <0B044CD5-B4F5-4614-B97A-E02E5C1E8A17@vmware.com> References: <20180604134713.101064-1-namit@vmware.com> <15813968.YrTFj7ZbY9@avalon> <0B044CD5-B4F5-4614-B97A-E02E5C1E8A17@vmware.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="UTF-8" Sender: linux-media-owner@vger.kernel.org List-ID: Hi Nadav, On Tuesday, 7 August 2018 03:58:05 EEST Nadav Amit wrote: > at 4:58 PM, Laurent Pinchart wrote: > > On Monday, 4 June 2018 16:47:13 EEST Nadav Amit wrote: > >=20 > >> The use of ALIGN() in uvc_alloc_entity() is incorrect, since the size = of > >> (entity->pads) is not a power of two. As a stop-gap, until a better > >> solution is adapted, use roundup() instead. > >>=20 > >> Found by a static assertion. Compile-tested only. > >>=20 > >> Fixes: 4ffc2d89f38a ("uvcvideo: Register subdevices for each entity") > >>=20 > >> Cc: Laurent Pinchart > >> Cc: Mauro Carvalho Chehab > >> Cc: linux-media@vger.kernel.org > >> Cc: linux-kernel@vger.kernel.org > >>=20 > >> Signed-off-by: Nadav Amit > >> --- > >> drivers/media/usb/uvc/uvc_driver.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >>=20 > >> diff --git a/drivers/media/usb/uvc/uvc_driver.c > >> b/drivers/media/usb/uvc/uvc_driver.c index 2469b49b2b30..6b989d41c034 > >> 100644 > >> --- a/drivers/media/usb/uvc/uvc_driver.c > >> +++ b/drivers/media/usb/uvc/uvc_driver.c > >> @@ -909,7 +909,7 @@ static struct uvc_entity *uvc_alloc_entity(u16 typ= e, > >> u8 id, > >> unsigned int size; > >> unsigned int i; > >>=20 > >> - extra_size =3D ALIGN(extra_size, sizeof(*entity->pads)); > >> + extra_size =3D roundup(extra_size, sizeof(*entity->pads)); > >> num_inputs =3D (type & UVC_TERM_OUTPUT) ? num_pads : num_pads - 1; > >> size =3D sizeof(*entity) + extra_size + sizeof(*entity->pads) * num_p= ads > >> + num_inputs; > >=20 > > The purpose of this alignment is to make sure that entity->pads will be= =20 > > properly aligned. In theory the size of uvc_entity should be taken into= =20 > > account too, but the structure contains pointers, so its size should > > already be properly aligned. This patch thus looks good to me. What > > made you say it's a stop-gap measure ? >=20 >=20 > Thanks. It=E2=80=99s been a while. Anyhow, I don=E2=80=99t know how =E2= =80=9Chot=E2=80=9D this code is, but > roundup uses a div operations, so if it is =E2=80=9Chot=E2=80=9D you may = want a different > way to align with lower overhead. >=20 > I presume it is not=E2=80=A6 You're right, it isn't. I'll include this patch in my next pull request for= =20 v4.20. =2D-=20 Regards, Laurent Pinchart