On Thu, 14 Oct 2021 at 19:20, Hans Verkuil <hverkuil-cisco@xxxxxxxxx> wrote:
>
> If CONFIG_MMU is not set, then copying ioctl arguments from userspace to kernelspace
> and vice versa will just work (access_ok() always returns true in that case), even if
> the argument is a NULL pointer.
>
> This is definitely a corner case that we want to check for, so add a NULL pointer check
> to the various core ioctl functions in the media frameworks.
>
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> Reported-by: Dillon Min <dillon.minfei@xxxxxxxxx>
> ---
> Note: this is an RFC only, this might fail if there are ioctls that pass a value as
> the ioctl argument instead of a pointer to a buffer. I know that that never happens for
> the V4L2, CEC and MC APIs, but I'm less certain about the DVB/RC APIs.
>
> Dillon, can you test if the v4l2-compliance VIDIOC_QUERYCAP(NULL) test now passes with
> this patch applied?
Sure, I will test this patch.
Best Regards
Dillon
>
> Thanks!
>
> Hans
> ---
> diff --git a/drivers/media/cec/core/cec-api.c b/drivers/media/cec/core/cec-api.c
> index 769e6b4cddce..b2498f0dd272 100644
> --- a/drivers/media/cec/core/cec-api.c
> +++ b/drivers/media/cec/core/cec-api.c
> @@ -511,6 +511,11 @@ static long cec_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> if (!cec_is_registered(adap))
> return -ENODEV;
>
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !arg)
> + return -EFAULT;
> +#endif
> +
> switch (cmd) {
> case CEC_ADAP_G_CAPS:
> return cec_adap_g_caps(adap, parg);
> diff --git a/drivers/media/dvb-core/dmxdev.c b/drivers/media/dvb-core/dmxdev.c
> index 5d5a48475a54..1ab0fe8df2d6 100644
> --- a/drivers/media/dvb-core/dmxdev.c
> +++ b/drivers/media/dvb-core/dmxdev.c
> @@ -1187,6 +1187,10 @@ static int dvb_demux_do_ioctl(struct file *file,
> static long dvb_demux_ioctl(struct file *file, unsigned int cmd,
> unsigned long arg)
> {
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !arg)
> + return -EFAULT;
> +#endif
> return dvb_usercopy(file, cmd, arg, dvb_demux_do_ioctl);
> }
>
> diff --git a/drivers/media/dvb-core/dvb_ca_en50221.c b/drivers/media/dvb-core/dvb_ca_en50221.c
> index 15a08d8c69ef..8ed33806fe13 100644
> --- a/drivers/media/dvb-core/dvb_ca_en50221.c
> +++ b/drivers/media/dvb-core/dvb_ca_en50221.c
> @@ -1422,6 +1422,10 @@ static int dvb_ca_en50221_io_do_ioctl(struct file *file,
> static long dvb_ca_en50221_io_ioctl(struct file *file,
> unsigned int cmd, unsigned long arg)
> {
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !arg)
> + return -EFAULT;
> +#endif
> return dvb_usercopy(file, cmd, arg, dvb_ca_en50221_io_do_ioctl);
> }
>
> diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
> index 258637d762d6..b21f28d6d6df 100644
> --- a/drivers/media/dvb-core/dvb_frontend.c
> +++ b/drivers/media/dvb-core/dvb_frontend.c
> @@ -2100,6 +2100,10 @@ static long dvb_frontend_ioctl(struct file *file, unsigned int cmd,
> if (!dvbdev)
> return -ENODEV;
>
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !arg)
> + return -EFAULT;
> +#endif
> return dvb_usercopy(file, cmd, arg, dvb_frontend_do_ioctl);
> }
>
> @@ -2136,6 +2140,10 @@ static int dvb_frontend_handle_compat_ioctl(struct file *file, unsigned int cmd,
> struct dvb_frontend_private *fepriv = fe->frontend_priv;
> int i, err = 0;
>
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !arg)
> + return -EFAULT;
> +#endif
> if (cmd == COMPAT_FE_SET_PROPERTY) {
> struct compat_dtv_properties prop, *tvps = NULL;
> struct compat_dtv_property *tvp = NULL;
> diff --git a/drivers/media/dvb-core/dvb_net.c b/drivers/media/dvb-core/dvb_net.c
> index dddebea644bb..97282946e35e 100644
> --- a/drivers/media/dvb-core/dvb_net.c
> +++ b/drivers/media/dvb-core/dvb_net.c
> @@ -1561,6 +1561,10 @@ static int dvb_net_do_ioctl(struct file *file,
> static long dvb_net_ioctl(struct file *file,
> unsigned int cmd, unsigned long arg)
> {
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !arg)
> + return -EFAULT;
> +#endif
> return dvb_usercopy(file, cmd, arg, dvb_net_do_ioctl);
> }
>
> diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
> index 795d9bfaba5c..f2311baadb00 100644
> --- a/drivers/media/dvb-core/dvbdev.c
> +++ b/drivers/media/dvb-core/dvbdev.c
> @@ -184,6 +184,10 @@ long dvb_generic_ioctl(struct file *file,
> if (!dvbdev)
> return -ENODEV;
>
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !arg)
> + return -EFAULT;
> +#endif
> if (!dvbdev->kernel_ioctl)
> return -EINVAL;
>
> diff --git a/drivers/media/mc/mc-device.c b/drivers/media/mc/mc-device.c
> index cf5e459b1d96..e25a407b6194 100644
> --- a/drivers/media/mc/mc-device.c
> +++ b/drivers/media/mc/mc-device.c
> @@ -445,6 +445,10 @@ static long media_device_ioctl(struct file *filp, unsigned int cmd,
> char __karg[256], *karg = __karg;
> long ret;
>
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !__arg)
> + return -EFAULT;
> +#endif
> if (_IOC_NR(cmd) >= ARRAY_SIZE(ioctl_info)
> || ioctl_info[_IOC_NR(cmd)].cmd != cmd)
> return -ENOIOCTLCMD;
> @@ -526,6 +530,10 @@ static long media_device_compat_ioctl(struct file *filp, unsigned int cmd,
> struct media_device *dev = devnode->media_dev;
> long ret;
>
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !arg)
> + return -EFAULT;
> +#endif
> switch (cmd) {
> case MEDIA_IOC_ENUM_LINKS32:
> mutex_lock(&dev->graph_mutex);
> diff --git a/drivers/media/mc/mc-request.c b/drivers/media/mc/mc-request.c
> index addb8f2d8939..0c1956899fcb 100644
> --- a/drivers/media/mc/mc-request.c
> +++ b/drivers/media/mc/mc-request.c
> @@ -223,6 +223,10 @@ static long media_request_ioctl(struct file *filp, unsigned int cmd,
> {
> struct media_request *req = filp->private_data;
>
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !arg)
> + return -EFAULT;
> +#endif
> switch (cmd) {
> case MEDIA_REQUEST_IOC_QUEUE:
> return media_request_ioctl_queue(req);
> diff --git a/drivers/media/pci/bt8xx/dst_ca.c b/drivers/media/pci/bt8xx/dst_ca.c
> index 85fcdc59f0d1..f7bd7a07606e 100644
> --- a/drivers/media/pci/bt8xx/dst_ca.c
> +++ b/drivers/media/pci/bt8xx/dst_ca.c
> @@ -532,6 +532,10 @@ static long dst_ca_ioctl(struct file *file, unsigned int cmd, unsigned long ioct
> void __user *arg = (void __user *)ioctl_arg;
> int result = 0;
>
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !ioctl_arg)
> + return -EFAULT;
> +#endif
> mutex_lock(&dst_ca_mutex);
> dvbdev = file->private_data;
> state = (struct dst_state *)dvbdev->priv;
> diff --git a/drivers/media/rc/lirc_dev.c b/drivers/media/rc/lirc_dev.c
> index 7f591ff5269d..9d89c68d2076 100644
> --- a/drivers/media/rc/lirc_dev.c
> +++ b/drivers/media/rc/lirc_dev.c
> @@ -372,6 +372,10 @@ static long lirc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> u32 val = 0;
> int ret;
>
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !arg)
> + return -EFAULT;
> +#endif
> if (_IOC_DIR(cmd) & _IOC_WRITE) {
> ret = get_user(val, argp);
> if (ret)
> diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> index 8176769a89fa..2bb8fa87aa46 100644
> --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> @@ -1254,6 +1254,11 @@ long v4l2_compat_ioctl32(struct file *file, unsigned int cmd, unsigned long arg)
> if (!video_is_registered(vdev))
> return -ENODEV;
>
> +#ifndef CONFIG_MMU
> + if (_IOC_DIR(cmd) != _IOC_NONE && !arg)
> + return -EFAULT;
> +#endif
> +
> if (_IOC_TYPE(cmd) == 'V' && _IOC_NR(cmd) < BASE_VIDIOC_PRIVATE)
> ret = file->f_op->unlocked_ioctl(file, cmd,
> (unsigned long)compat_ptr(arg));
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 31d0109ce5a8..d4ec18fd1770 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -3279,6 +3279,10 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
>
> /* Copy arguments into temp kernel buffer */
> if (_IOC_DIR(cmd) != _IOC_NONE) {
> +#ifndef CONFIG_MMU
> + if (!arg)
> + return -EFAULT;
> +#endif
> if (ioc_size <= sizeof(sbuf)) {
> parg = sbuf;
> } else {
