Re: [PATCH v5 6/8] media: v4l2-core: fix v4l2_buffer handling for time64 ABI

[Arnd Bergmann <arnd@arndb.de>]

On Thu, Dec 12, 2019 at 4:43 PM Hans Verkuil <hverkuil@xs4all.nl> wrote:
>
> On 11/26/19 5:18 PM, Arnd Bergmann wrote:
> >
> >       switch (cmd) {
> > +#ifdef COMPAT_32BIT_TIME
>
> COMPAT_32BIT_TIME -> CONFIG_COMPAT_32BIT_TIME

Fixed.

> > +             *vb = (struct v4l2_buffer) {
> > +                     .index          = vb32.index,
> > +                     .type           = vb32.type,
> > +                     .bytesused      = vb32.bytesused,
> > +                     .flags          = vb32.flags,
> > +                     .field          = vb32.field,
> > +                     .timestamp.tv_sec       = vb32.timestamp.tv_sec,
> > +                     .timestamp.tv_usec      = vb32.timestamp.tv_usec,
> > +                     .timecode       = vb32.timecode,
>
> You forgot to copy sequence.
>
> > +                     .memory         = vb32.memory,
> > +                     .m.userptr      = vb32.m.usercopy,
>
> usercopy -> userptr

Fixed.

> > +                     .length         = vb32.length,
> > +                     .request_fd     = vb32.request_fd,
> > +             };
> > +
> > +             if (cmd == VIDIOC_QUERYBUF_TIME32)
> > +                     memset(&vb->length, 0, sizeof(*vb) -
> > +                            offsetof(struct v4l2_buffer, length));
>
> It's from the field AFTER vb->length that this needs to be zeroed. It's best to
> use the CLEAR_AFTER_FIELD macro here.

I'm a bit lost about this one: the fields that are not explicitly
uninitialized here are already set to zero by the assignment
above. Should this simply be a

                if (cmd == VIDIOC_QUERYBUF_TIME32)
                       vb->request_fd = 0;

then? I don't remember where that memset() originally came
from or why request_fd has to be cleared here.

> > @@ -3100,6 +3141,30 @@ static int video_put_user(void __user *arg, void *parg, unsigned int cmd)
> >                       return -EFAULT;
> >               break;
> >       }
> > +     case VIDIOC_QUERYBUF_TIME32:
> > +     case VIDIOC_QBUF_TIME32:
> > +     case VIDIOC_DQBUF_TIME32:
> > +     case VIDIOC_PREPARE_BUF_TIME32: {
> > +             struct v4l2_buffer *vb = parg;
> > +             struct v4l2_buffer_time32 vb32 = {
> > +                     .index          = vb->index,
> > +                     .type           = vb->type,
> > +                     .bytesused      = vb->bytesused,
> > +                     .flags          = vb->flags,
> > +                     .field          = vb->field,
> > +                     .timestamp.tv_sec       = vb->timestamp.tv_sec,
> > +                     .timestamp.tv_usec      = vb->timestamp.tv_usec,
> > +                     .timecode       = vb->timecode,
>
> You forgot to copy sequence.

Fixed.

> With these changes this patch series passed both the 64 and 32 bit compliance
> tests (in fact, all the issues mentioned above were found with these compliance
> tests).

Yay compliance tests!

> I am unable to test with musl since v4l2-ctl and v4l2-compliance are C++ programs,
> and there doesn't appear to be an easy way to compile a C++ program with musl.
>
> If you happen to have a test environment where you can compile C++ with musl,
> then let me know and I can give instructions on how to run the compliance tests.
>
> If you can't test that, then I can merge this regardless, and hope for the best
> once the Y2038 fixes end up in glibc. But ideally I'd like to have this tested.

I've heard good things about the prebuilt toolchains from http://musl.cc/.
These seems to come with a libstdc++, but I have not tried that myself.

I've folded the change below into this patch in my y2038-v4l2-v6 branch
but have not been able to update the copy on git.kernel.org yet because of
server-side issues today.

          Arnd

8<-----
diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c
b/drivers/media/v4l2-core/v4l2-ioctl.c
index c416870a3166..667225712343 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -3055,7 +3055,7 @@ static int video_get_user(void __user *arg, void
*parg, unsigned int cmd,
        }

        switch (cmd) {
-#ifdef COMPAT_32BIT_TIME
+#ifdef CONFIG_COMPAT_32BIT_TIME
        case VIDIOC_QUERYBUF_TIME32:
        case VIDIOC_QBUF_TIME32:
        case VIDIOC_DQBUF_TIME32:
@@ -3075,15 +3075,15 @@ static int video_get_user(void __user *arg,
void *parg, unsigned int cmd,
                        .timestamp.tv_sec       = vb32.timestamp.tv_sec,
                        .timestamp.tv_usec      = vb32.timestamp.tv_usec,
                        .timecode       = vb32.timecode,
+                       .sequence       = vb32.sequence,
                        .memory         = vb32.memory,
-                       .m.userptr      = vb32.m.usercopy,
+                       .m.userptr      = vb32.m.userptr,
                        .length         = vb32.length,
                        .request_fd     = vb32.request_fd,
                };

                if (cmd == VIDIOC_QUERYBUF_TIME32)
-                       memset(&vb->length, 0, sizeof(*vb) -
-                              offsetof(struct v4l2_buffer, length));
+                       vb->request_fd = 0;

                break;
        }
@@ -3155,6 +3155,7 @@ static int video_put_user(void __user *arg, void
*parg, unsigned int cmd)
                        .timestamp.tv_sec       = vb->timestamp.tv_sec,
                        .timestamp.tv_usec      = vb->timestamp.tv_usec,
                        .timecode       = vb->timecode,
+                       .sequence       = vb->sequence,
                        .memory         = vb->memory,
                        .m.userptr      = vb->m.userptr,
                        .length         = vb->length,