From: Arnd Bergmann <arnd@arndb.de>
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>,
Linux Media Mailing List <linux-media@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
y2038 Mailman List <y2038@lists.linaro.org>
Subject: Re: [PATCH v4 5/8] media: v4l2-core: fix VIDIOC_DQEVENT for time64 ABI
Date: Tue, 26 Nov 2019 15:43:42 +0100 [thread overview]
Message-ID: <CAK8P3a3vHWBJU6EiUbRKJ01Zsv5E5Yfr+=h2Dg95atjvaHZ+Rg@mail.gmail.com> (raw)
In-Reply-To: <272c471b-a7a9-c830-e19b-d1f19ee47073@xs4all.nl>
On Mon, Nov 25, 2019 at 3:40 PM Hans Verkuil <hverkuil@xs4all.nl> wrote:
> On 11/11/19 9:38 PM, Arnd Bergmann wrote:
> > switch (cmd) {
> > +#ifdef CONFIG_COMPAT_32BIT_TIME
> > + case VIDIOC_DQEVENT_TIME32: {
> > + struct v4l2_event_time32 ev32;
> > + struct v4l2_event *ev = parg;
> > +
> > + memcpy(&ev32, ev, offsetof(struct v4l2_event, timestamp));
> > + ev32.timestamp.tv_sec = ev->timestamp.tv_sec;
> > + ev32.timestamp.tv_nsec = ev->timestamp.tv_nsec;
> > + memcpy(&ev32.id, &ev->id, sizeof(*ev) - offsetof(struct v4l2_event, id));
>
> This looks dangerous: due to 64-bit alignment requirements the
> v4l2_event struct may end with a 4-byte hole at the end of the struct,
> which you do not want to copy to ev32.
>
> I think it is safer to just copy id and reserved separately:
>
> ev32.id = ev->id;
> memcpy(ev32.reserved, ev->reserved, sizeof(ev->reserved));
Actually I think it's that's also bad: The padding in *ev must already be
cleared here (otherwise there is a leak of stack data in the kernel
already), so *not* copying the padding requires at least adding a memset
upfront.
I would do the per-member copy like I did for v4l2_buffer in my
other reply:
struct v4l2_event *ev = parg;
struct v4l2_event_time32 ev32 = {
.type = ev->type,
.pending = ev->pending,
.sequence = ev->sequence,
.timestamp.tv_sec = ev->timestamp.tv_sec,
.timestamp.tv_nsec = ev->timestamp.tv_nsec,
.id = ev->id,
};
memcpy(ev32.u, ev->u, sizeof(ev->u));
memcpy(ev32.reserved, ev->reserved, sizeof(ev->reserved));
if (copy_to_user(arg, &ev32, sizeof(ev32)))
return -EFAULT;
Unfortunately this is a little uglier because it still requires the two
memcpy() for the arrays, but I think it's good enough.
Any other ideas? Let me know if I should do a memset()
plus individual member copy instead.
> > + if (!(sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS))
> > + return -ENOIOCTLCMD;
> > +
> > + rval = v4l2_event_dequeue(vfh, &ev, file->f_flags & O_NONBLOCK);
> > +
> > + memcpy(ev32, &ev, offsetof(struct v4l2_event, timestamp));
> > + ev32->timestamp.tv_sec = ev.timestamp.tv_sec;
> > + ev32->timestamp.tv_nsec = ev.timestamp.tv_nsec;
> > + memcpy(&ev32->id, &ev.id,
> > + sizeof(ev) - offsetof(struct v4l2_event, id));
>
> Ditto.
Using the corresponding code here as well.
> > +
> > #define V4L2_EVENT_SUB_FL_SEND_INITIAL (1 << 0)
> > #define V4L2_EVENT_SUB_FL_ALLOW_FEEDBACK (1 << 1)
> >
> > @@ -2486,6 +2515,7 @@ struct v4l2_create_buffers {
> > #define VIDIOC_S_DV_TIMINGS _IOWR('V', 87, struct v4l2_dv_timings)
> > #define VIDIOC_G_DV_TIMINGS _IOWR('V', 88, struct v4l2_dv_timings)
> > #define VIDIOC_DQEVENT _IOR('V', 89, struct v4l2_event)
> > +#define VIDIOC_DQEVENT_TIME32 _IOR('V', 89, struct v4l2_event_time32)
>
> Shouldn't this be under #ifdef __KERNEL__?
>
> And should this be in the public header at all? media/v4l2-ioctl.h might be a better
> place.
Done.
Arnd
next prev parent reply other threads:[~2019-11-26 14:44 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-11 20:38 [PATCH v4 0/8] y2038 safety in v4l2 Arnd Bergmann
2019-11-11 20:38 ` [PATCH v4 1/8] media: documentation: fix video_event description Arnd Bergmann
2019-11-11 20:38 ` [PATCH v4 2/8] media: v4l2: abstract timeval handling in v4l2_buffer Arnd Bergmann
2019-11-25 15:52 ` Hans Verkuil
2019-11-26 11:34 ` Arnd Bergmann
2019-11-26 11:43 ` Hans Verkuil
2019-11-26 12:42 ` Arnd Bergmann
2019-11-11 20:38 ` [PATCH v4 3/8] media: v4l2-core: compat: ignore native command codes Arnd Bergmann
2019-11-11 20:38 ` [PATCH v4 4/8] media: v4l2-core: split out data copy from video_usercopy Arnd Bergmann
2019-11-11 20:38 ` [PATCH v4 5/8] media: v4l2-core: fix VIDIOC_DQEVENT for time64 ABI Arnd Bergmann
2019-11-25 14:40 ` Hans Verkuil
2019-11-26 14:43 ` Arnd Bergmann [this message]
2019-11-26 15:10 ` Hans Verkuil
2019-11-26 15:19 ` Arnd Bergmann
2019-11-11 20:38 ` [PATCH v4 6/8] media: v4l2-core: fix v4l2_buffer handling " Arnd Bergmann
2019-11-25 14:57 ` Hans Verkuil
2019-11-26 13:50 ` Arnd Bergmann
2019-11-26 14:15 ` Hans Verkuil
2019-11-26 15:17 ` Arnd Bergmann
2019-11-26 15:24 ` Hans Verkuil
2019-11-11 20:38 ` [PATCH v4 7/8] media: v4l2-core: fix compat VIDIOC_DQEVENT " Arnd Bergmann
2019-11-11 20:38 ` [PATCH v4 8/8] media: v4l2-core: fix compat v4l2_buffer handling " Arnd Bergmann
2019-11-25 16:02 ` [PATCH v4 0/8] y2038 safety in v4l2 Hans Verkuil
2019-11-26 11:13 ` Arnd Bergmann
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