Quoting Mark Thompson (2020-04-12 16:46:25)
> If we have both root and DRM master then drop the latter because we
> don't need both and holding onto it can interfere with running other
> programs.
>
> From a discussion with deltasquared on IRC.
> ---
> It would be marginally better to check whether we have CAP_SYS_ADMIN rather
> than just whether we are effectively root, but the capabilities interface is
> a lot more complex to query and this is already sufficient to cover the
> reported case.
>
> libavdevice/kmsgrab.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/libavdevice/kmsgrab.c b/libavdevice/kmsgrab.c
> index d0de774871..53280da0f5 100644
> --- a/libavdevice/kmsgrab.c
> +++ b/libavdevice/kmsgrab.c
> @@ -263,6 +263,13 @@ static av_cold int kmsgrab_read_header(AVFormatContext
> *avctx)
> ctx->device = (AVHWDeviceContext*) ctx->device_ref->data;
> ctx->hwctx = (AVDRMDeviceContext*)ctx->device->hwctx;
>
> + if (geteuid() == 0 && drmIsMaster(ctx->hwctx->fd)) {
> + // If we have both root and DRM master then drop the latter
> + // because we don't need both and holding onto it can interfere
> + // with running other programs.
> + drmDropMaster(ctx->hwctx->fd);
> + }
Any idea how would this interact with user namespaces?
--
Anton Khirnov
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