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Message-ID: <d54c82b5-21b7-2d5e-ad0b-206527ad2768@xs4all.nl>
Date: Mon, 25 Nov 2019 15:57:53 +0100
From: Hans Verkuil <hverkuil@...all.nl>
To: Arnd Bergmann <arnd@...db.de>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
linux-media@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, y2038@...ts.linaro.org
Subject: Re: [PATCH v4 6/8] media: v4l2-core: fix v4l2_buffer handling for
time64 ABI
On 11/11/19 9:38 PM, Arnd Bergmann wrote:
> The v4l2_buffer structure contains a 'struct timeval' member that is
> defined by the user space C library, creating an ABI incompatibility
> when that gets updated to a 64-bit time_t.
>
> As in v4l2_event, handle this with a special case in video_put_user()
> and video_get_user() to replace the memcpy there.
>
> Since the structure also contains a pointer, there are now two
> native versions (on 32-bit systems) as well as two compat versions
> (on 64-bit systems), which unfortunately complicates the compat
> handler quite a bit.
>
> Duplicating the existing handlers for the new types is a safe
> conversion for now, but unfortunately this may turn into a
> maintenance burden later. A larger-scale rework of the
> compat code might be a better alternative, but is out of scope
> of the y2038 work.
>
> Sparc64 needs a special case because of their special suseconds_t
> definition.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> drivers/media/v4l2-core/v4l2-ioctl.c | 57 ++++++++++++++++++++++++++--
> include/uapi/linux/videodev2.h | 45 ++++++++++++++++++++++
> 2 files changed, 98 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 1de939d11628..4ae1bcaec3fa 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -474,10 +474,10 @@ static void v4l_print_buffer(const void *arg, bool write_only)
> const struct v4l2_plane *plane;
> int i;
>
> - pr_cont("%02ld:%02d:%02d.%08ld index=%d, type=%s, request_fd=%d, flags=0x%08x, field=%s, sequence=%d, memory=%s",
> - p->timestamp.tv_sec / 3600,
> - (int)(p->timestamp.tv_sec / 60) % 60,
> - (int)(p->timestamp.tv_sec % 60),
> + pr_cont("%02d:%02d:%02d.%09ld index=%d, type=%s, request_fd=%d, flags=0x%08x, field=%s, sequence=%d, memory=%s",
> + (int)p->timestamp.tv_sec / 3600,
> + ((int)p->timestamp.tv_sec / 60) % 60,
> + ((int)p->timestamp.tv_sec % 60),
> (long)p->timestamp.tv_usec,
> p->index,
> prt_names(p->type, v4l2_type_names), p->request_fd,
> @@ -3014,6 +3014,14 @@ static unsigned int video_translate_cmd(unsigned int cmd)
> #ifdef CONFIG_COMPAT_32BIT_TIME
> case VIDIOC_DQEVENT_TIME32:
> return VIDIOC_DQEVENT;
> + case VIDIOC_QUERYBUF_TIME32:
> + return VIDIOC_QUERYBUF;
> + case VIDIOC_QBUF_TIME32:
> + return VIDIOC_QBUF;
> + case VIDIOC_DQBUF_TIME32:
> + return VIDIOC_DQBUF;
> + case VIDIOC_PREPARE_BUF_TIME32:
> + return VIDIOC_PREPARE_BUF;
> #endif
> }
>
> @@ -3032,6 +3040,30 @@ static int video_get_user(void __user *arg, void *parg, unsigned int cmd,
> }
>
> switch (cmd) {
> +#ifdef COMPAT_32BIT_TIME
> + case VIDIOC_QUERYBUF_TIME32:
> + case VIDIOC_QBUF_TIME32:
> + case VIDIOC_DQBUF_TIME32:
> + case VIDIOC_PREPARE_BUF_TIME32: {
> + struct v4l2_buffer_time32 vb32;
> + struct v4l2_buffer *vb = parg;
> +
> + if (copy_from_user(&vb32, arg, sizeof(vb32)))
> + return -EFAULT;
> +
> + memcpy(vb, &vb32, offsetof(struct v4l2_buffer, timestamp));
> + vb->timestamp.tv_sec = vb32.timestamp.tv_sec;
> + vb->timestamp.tv_usec = vb32.timestamp.tv_usec;
> + memcpy(&vb->timecode, &vb32.timecode,
> + sizeof(*vb) - offsetof(struct v4l2_buffer, timecode));
I have similar concerns as with dqevent about whether this memcpy is the right approach.
Unless you can prove with a utility like pahole that this memcpy is safe.
> +
> + if (cmd == VIDIOC_QUERYBUF_TIME32)
> + memset(&vb->length, 0, sizeof(*vb) -
> + offsetof(struct v4l2_buffer, length));
> +
> + break;
> + }
> +#endif
> default:
> /*
> * In some cases, only a few fields are used as input,
> @@ -3080,6 +3112,23 @@ 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_time32 vb32;
> + struct v4l2_buffer *vb = parg;
> +
> + memcpy(&vb32, vb, offsetof(struct v4l2_buffer, timestamp));
> + vb32.timestamp.tv_sec = vb->timestamp.tv_sec;
> + vb32.timestamp.tv_usec = vb->timestamp.tv_usec;
> + memcpy(&vb32.timecode, &vb->timecode,
> + sizeof(*vb) - offsetof(struct v4l2_buffer, timecode));
Ditto.
> +
> + if (copy_to_user(arg, &vb32, sizeof(vb32)))
> + return -EFAULT;
> + break;
> + }
> #endif
> default:
> /* Copy results into user buffer */
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 1d2553d4ed5b..f05c54d63f96 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -990,7 +990,47 @@ struct v4l2_buffer {
> __u32 bytesused;
> __u32 flags;
> __u32 field;
> +#ifdef __KERNEL__
> + /* match glibc timeval64 format */
> + struct {
> + long long tv_sec;
> +# if defined(__sparc__) && defined(__arch64__)
> + int tv_usec;
> + int __pad;
> +# else
> + long long tv_usec;
> +# endif
> + } timestamp;
Ewww!
Are there more places where this is needed? If so, then I very much prefer
that a __kernel_timeval struct is defined somewhere, with appropriate
comments.
> +#else
> struct timeval timestamp;
> +#endif
> + struct v4l2_timecode timecode;
> + __u32 sequence;
> +
> + /* memory location */
> + __u32 memory;
> + union {
> + __u32 offset;
> + unsigned long userptr;
> + struct v4l2_plane *planes;
> + __s32 fd;
> + } m;
> + __u32 length;
> + __u32 reserved2;
> + union {
> + __s32 request_fd;
> + __u32 reserved;
> + };
> +};
> +
> +#ifdef __KERNEL__
> +struct v4l2_buffer_time32 {
> + __u32 index;
> + __u32 type;
> + __u32 bytesused;
> + __u32 flags;
> + __u32 field;
> + struct old_timeval32 timestamp;
> struct v4l2_timecode timecode;
> __u32 sequence;
>
> @@ -1009,6 +1049,7 @@ struct v4l2_buffer {
> __u32 reserved;
> };
> };
> +#endif
Can this be moved to v4l2-ioctls.h?
>
> #ifndef __KERNEL__
> /**
> @@ -2446,12 +2487,15 @@ struct v4l2_create_buffers {
> #define VIDIOC_S_FMT _IOWR('V', 5, struct v4l2_format)
> #define VIDIOC_REQBUFS _IOWR('V', 8, struct v4l2_requestbuffers)
> #define VIDIOC_QUERYBUF _IOWR('V', 9, struct v4l2_buffer)
> +#define VIDIOC_QUERYBUF_TIME32 _IOWR('V', 9, struct v4l2_buffer_time32)
And all these should be moved there as well.
> #define VIDIOC_G_FBUF _IOR('V', 10, struct v4l2_framebuffer)
> #define VIDIOC_S_FBUF _IOW('V', 11, struct v4l2_framebuffer)
> #define VIDIOC_OVERLAY _IOW('V', 14, int)
> #define VIDIOC_QBUF _IOWR('V', 15, struct v4l2_buffer)
> +#define VIDIOC_QBUF_TIME32 _IOWR('V', 15, struct v4l2_buffer_time32)
> #define VIDIOC_EXPBUF _IOWR('V', 16, struct v4l2_exportbuffer)
> #define VIDIOC_DQBUF _IOWR('V', 17, struct v4l2_buffer)
> +#define VIDIOC_DQBUF_TIME32 _IOWR('V', 17, struct v4l2_buffer_time32)
> #define VIDIOC_STREAMON _IOW('V', 18, int)
> #define VIDIOC_STREAMOFF _IOW('V', 19, int)
> #define VIDIOC_G_PARM _IOWR('V', 21, struct v4l2_streamparm)
> @@ -2520,6 +2564,7 @@ struct v4l2_create_buffers {
> #define VIDIOC_UNSUBSCRIBE_EVENT _IOW('V', 91, struct v4l2_event_subscription)
> #define VIDIOC_CREATE_BUFS _IOWR('V', 92, struct v4l2_create_buffers)
> #define VIDIOC_PREPARE_BUF _IOWR('V', 93, struct v4l2_buffer)
> +#define VIDIOC_PREPARE_BUF_TIME32 _IOWR('V', 93, struct v4l2_buffer_time32)
> #define VIDIOC_G_SELECTION _IOWR('V', 94, struct v4l2_selection)
> #define VIDIOC_S_SELECTION _IOWR('V', 95, struct v4l2_selection)
> #define VIDIOC_DECODER_CMD _IOWR('V', 96, struct v4l2_decoder_cmd)
>
Regards,
Hans
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