Hi Hans,
On Mon, Mar 21, 2022 at 01:34:05PM +0100, Hans Verkuil wrote:
> On 21/03/2022 12:53, Laurent Pinchart wrote:
> > On Mon, Mar 21, 2022 at 12:03:30PM +0100, Hans Verkuil wrote:
> >> If allocating array_buf fails, or copying data from userspace into that
> >> buffer fails, then just free memory and return the error. Don't attempt
> >> to call video_put_user() since there is no point.
> >>
> >> If writing the array back to userspace fails, then don't go to out_array_args,
> >> instead just continue with the regular code that just returns the error
> >> unless 'always_copy' is set. That flag was just completely ignored when
> >> writing back the array data.
> >>
> >> Update the VIDIOC_G/S/TRY_EXT_CTRLS ioctls to set the ALWAYS_COPY flag
> >> since they now need it.
> >>
> >> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> >> ---
> >> Changes since v1:
> >> - drop the now unused out_array_args label
> >> - set the INFO_FL_ALWAYS_COPY for the VIDIOC_G/S/TRY_EXT_CTRLS ioctls
> >> ---
> >> drivers/media/v4l2-core/v4l2-ioctl.c | 12 +++++-------
> >> 1 file changed, 5 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> >> index 96e307fe3aab..3eb8f5f0958d 100644
> >> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> >> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> >> @@ -2816,9 +2816,9 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = {
> >> IOCTL_INFO(VIDIOC_S_PRIORITY, v4l_s_priority, v4l_print_u32, INFO_FL_PRIO),
> >> IOCTL_INFO(VIDIOC_G_SLICED_VBI_CAP, v4l_g_sliced_vbi_cap, v4l_print_sliced_vbi_cap, INFO_FL_CLEAR(v4l2_sliced_vbi_cap, type)),
> >> IOCTL_INFO(VIDIOC_LOG_STATUS, v4l_log_status, v4l_print_newline, 0),
> >> - IOCTL_INFO(VIDIOC_G_EXT_CTRLS, v4l_g_ext_ctrls, v4l_print_ext_controls, INFO_FL_CTRL),
> >> - IOCTL_INFO(VIDIOC_S_EXT_CTRLS, v4l_s_ext_ctrls, v4l_print_ext_controls, INFO_FL_PRIO | INFO_FL_CTRL),
> >> - IOCTL_INFO(VIDIOC_TRY_EXT_CTRLS, v4l_try_ext_ctrls, v4l_print_ext_controls, INFO_FL_CTRL),
> >> + IOCTL_INFO(VIDIOC_G_EXT_CTRLS, v4l_g_ext_ctrls, v4l_print_ext_controls, INFO_FL_CTRL | INFO_FL_ALWAYS_COPY),
> >> + IOCTL_INFO(VIDIOC_S_EXT_CTRLS, v4l_s_ext_ctrls, v4l_print_ext_controls, INFO_FL_PRIO | INFO_FL_CTRL | INFO_FL_ALWAYS_COPY),
> >> + IOCTL_INFO(VIDIOC_TRY_EXT_CTRLS, v4l_try_ext_ctrls, v4l_print_ext_controls, INFO_FL_CTRL | INFO_FL_ALWAYS_COPY),
> >> IOCTL_INFO(VIDIOC_ENUM_FRAMESIZES, v4l_stub_enum_framesizes, v4l_print_frmsizeenum, INFO_FL_CLEAR(v4l2_frmsizeenum, pixel_format)),
> >> IOCTL_INFO(VIDIOC_ENUM_FRAMEINTERVALS, v4l_stub_enum_frameintervals, v4l_print_frmivalenum, INFO_FL_CLEAR(v4l2_frmivalenum, height)),
> >> IOCTL_INFO(VIDIOC_G_ENC_INDEX, v4l_stub_g_enc_index, v4l_print_enc_idx, 0),
> >> @@ -3311,7 +3311,7 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
> >> array_buf = kvmalloc(array_size, GFP_KERNEL);
> >> err = -ENOMEM;
> >> if (array_buf == NULL)
> >> - goto out_array_args;
> >> + goto out;
> >> err = -EFAULT;
> >> if (in_compat_syscall())
> >> err = v4l2_compat_get_array_args(file, array_buf,
> >> @@ -3321,7 +3321,7 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
> >> err = copy_from_user(array_buf, user_ptr, array_size) ?
> >> -EFAULT : 0;
> >> if (err)
> >> - goto out_array_args;
> >> + goto out;
> >> *kernel_ptr = array_buf;
> >> }
> >>
> >> @@ -3353,7 +3353,6 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
> >> } else if (copy_to_user(user_ptr, array_buf, array_size)) {
> >> err = -EFAULT;
> >> }
> >> - goto out_array_args;
> >> }
> >> /*
> >> * Some ioctls can return an error, but still have valid
> >> @@ -3362,7 +3361,6 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
> >> if (err < 0 && !always_copy)
> >> goto out;
> >>
> >> -out_array_args:
> >> if (video_put_user((void __user *)arg, parg, cmd, orig_cmd))
> >> err = -EFAULT;
> >
> > Could we turn this into
> >
> > if (err >= 0 || always_copy) {
> > if (video_put_user((void __user *)arg, parg, cmd, orig_cmd))
> > err = -EFAULT;
> > }
> >
> > to avoid the goto ?
> >
> > With this,
> >
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> >
> > I also wonder if we should skip the copy to user for the array args when
> > an error occurs (unless always_copy is set). What do you think ? It's
> > not a candidate for this patch of course.
>
> Actually, that's a very good point and I think it belongs to this patch as well.
> It's really wrong to copy back data on error unless always_copy is set.
>
> But in that case I prefer to keep the goto: the 'if (err < 0 && !always_copy)'
> just moves up to before the 'if (has_array_args) {':
>
> That part of the patch will then look like this:
>
> @@ -3339,6 +3339,13 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
> trace_v4l2_qbuf(video_devdata(file)->minor, parg);
> }
>
> + /*
> + * Some ioctls can return an error, but still have valid
> + * results that must be returned.
> + */
> + if (err < 0 && !always_copy)
> + goto out;
> +
> if (has_array_args) {
> *kernel_ptr = (void __force *)user_ptr;
> if (in_compat_syscall()) {
> @@ -3353,16 +3360,8 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
> } else if (copy_to_user(user_ptr, array_buf, array_size)) {
> err = -EFAULT;
> }
> - goto out_array_args;
> }
> - /*
> - * Some ioctls can return an error, but still have valid
> - * results that must be returned.
> - */
> - if (err < 0 && !always_copy)
> - goto out;
>
> -out_array_args:
> if (video_put_user((void __user *)arg, parg, cmd, orig_cmd))
> err = -EFAULT;
> out:
No objection.
--
Regards,
Laurent Pinchart
