Subject: Re: [PATCH v3 1/4] drm/ras: Introduce the DRM RAS infrastructure over generic netlink

From: Rodrigo Vivi <[email-masked]>
Date: Fri, 16 Jan 2026 15:26:38 -0500

On Fri, Jan 16, 2026 at 11:26:36AM +0530, Riana Tauro wrote:
> 
> 
> On 1/16/2026 5:09 AM, Zack McKevitt wrote:
> > 
> > 
> > On 1/13/2026 1:20 AM, Riana Tauro wrote:
> > > > > > > diff --git
> > > > > > > a/Documentation/netlink/specs/drm_ras.yaml b/
> > > > > > > Documentation/netlink/specs/drm_ras.yaml
> > > > > > > new file mode 100644
> > > > > > > index 000000000000..be0e379c5bc9
> > > > > > > --- /dev/null
> > > > > > > +++ b/Documentation/netlink/specs/drm_ras.yaml
> > > > > > > @@ -0,0 +1,130 @@
> > > > > > > +# SPDX-License-Identifier: ((GPL-2.0 WITH
> > > > > > > Linux-syscall-note) OR BSD-3-Clause)
> > > > > > > +---
> > > > > > > +name: drm-ras
> > > > > > > +protocol: genetlink
> > > > > > > +uapi-header: drm/drm_ras.h
> > > > > > > +
> > > > > > > +doc: >-
> > > > > > > +  DRM RAS (Reliability, Availability,
> > > > > > > Serviceability) over Generic Netlink.
> > > > > > > +  Provides a standardized mechanism for DRM drivers
> > > > > > > to register "nodes"
> > > > > > > +  representing hardware/software components capable
> > > > > > > of reporting error counters.
> > > > > > > +  Userspace tools can query the list of nodes or
> > > > > > > individual error counters
> > > > > > > +  via the Generic Netlink interface.
> > > > > > > +
> > > > > > > +definitions:
> > > > > > > +  -
> > > > > > > +    type: enum
> > > > > > > +    name: node-type
> > > > > > > +    value-start: 1
> > > > > > > +    entries: [error-counter]
> > > > > > > +    doc: >-
> > > > > > > +         Type of the node. Currently, only error-counter nodes are
> > > > > > > +         supported, which expose reliability
> > > > > > > counters for a hardware/software
> > > > > > > +         component.
> > > > > > > +
> > > > > > > +attribute-sets:
> > > > > > > +  -
> > > > > > > +    name: node-attrs
> > > > > > > +    attributes:
> > > > > > > +      -
> > > > > > > +        name: node-id
> > > > > > > +        type: u32
> > > > > > > +        doc: >-
> > > > > > > +             Unique identifier for the node.
> > > > > > > +             Assigned dynamically by the DRM RAS
> > > > > > > core upon registration.
> > > > > > > +      -
> > > > > > > +        name: device-name
> > > > > > > +        type: string
> > > > > > > +        doc: >-
> > > > > > > +             Device name chosen by the driver at registration.
> > > > > > > +             Can be a PCI BDF, UUID, or module name if unique.
> > > > > > > +      -
> > > > > > > +        name: node-name
> > > > > > > +        type: string
> > > > > > > +        doc: >-
> > > > > > > +             Node name chosen by the driver at registration.
> > > > > > > +             Can be an IP block name, or any name
> > > > > > > that identifies the
> > > > > > > +             RAS node inside the device.
> > > > > > > +      -
> > > > > > > +        name: node-type
> > > > > > > +        type: u32
> > > > > > > +        doc: Type of this node, identifying its function.
> > > > > > > +        enum: node-type
> > > > > > > +  -
> > > > > > > +    name: error-counter-attrs
> > > > > > > +    attributes:
> > > > > > > +      -
> > > > > > > +        name: node-id
> > > > > > > +        type: u32
> > > > > > > +        doc:  Node ID targeted by this error counter operation.
> > > > > > > +      -
> > > > > > > +        name: error-id
> > > > > > > +        type: u32
> > > > > > > +        doc: Unique identifier for a specific error
> > > > > > > counter within an node.
> > > > > > > +      -
> > > > > > > +        name: error-name
> > > > > > > +        type: string
> > > > > > > +        doc: Name of the error.
> > > > > > > +      -
> > > > > > > +        name: error-value
> > > > > > > +        type: u32
> > > > > > > +        doc: Current value of the requested error counter.
> > > > > > > +
> > > > > > > +operations:
> > > > > > > +  list:
> > > > > > > +    -
> > > > > > > +      name: list-nodes
> > > > > > > +      doc: >-
> > > > > > > +           Retrieve the full list of currently
> > > > > > > registered DRM RAS nodes.
> > > > > > > +           Each node includes its dynamically
> > > > > > > assigned ID, name, and type.
> > > > > > > +           **Important:** User space must call this
> > > > > > > operation first to obtain
> > > > > > > +           the node IDs. These IDs are required for all subsequent
> > > > > > > +           operations on nodes, such as querying error counters.
> > > > > 
> > > > > I am curious about security implications of this design.
> > > > 
> > > > hmm... very good point you are raising here.
> > > > 
> > > > This current design relies entirely in the CAP_NET_ADMIN.
> > > > No driver would have the flexibility to choose anything differently.
> > > > Please notice that the flag admin-perm is hardcoded in this yaml file.
> > > > 
> > > > > If the complete
> > > > > list of RAS nodes is visible for any process on the system
> > > > > (and one wants to
> > > > > avoid requiring CAP_NET_ADMIN), there should be some way to enforce
> > > > > permission checks when performing these operations if desired.
> > > > 
> > > > Right now, there's no way that the driver would choose not avoid
> > > > requiring
> > > > CAP_NET_ADMIN...
> > > > 
> > > > Only way would be the admin to give the cap_net_admin to the tool with:
> > > > 
> > > > $ sudo setcap cap_net_admin+ep /bin/drm_ras_tool
> > > > 
> > > > but not ideal and not granular anyway...
> > > > 
> > > > > 
> > > > > For example, this might be implemented in the driver's definition of
> > > > > callback functions like query_error_counter; some drivers
> > > > > may want to ensure
> > > > > that the process can in fact open the file descriptor
> > > > > corresponding to the
> > > > > queried device before serving a netlink request. Is it
> > > > > enough for a driver
> > > > > to simply return -EPERM in this case? Any driver that doesnt
> > > > > wish to protect
> > > > > its RAS nodes need not implement checks in their callbacks.
> > > > 
> > > > Fair enough. If we want to give the option to the drivers, then we need:
> > > > 
> > > > 1. to first remove all the admin-perm flags below and leave the
> > > > driver to
> > > > pick up their policy on when to return something or -EPERM.
> > > > 2. Document this security responsibility and list a few possibilities.
> > > > 3. In our Xe case here I believe the easiest option is to use
> > > > something like:
> > > > 
> > > > struct scm_creds *creds = NETLINK_CREDS(cb->skb);
> > > > if (!gid_eq(creds->gid, GLOBAL_ROOT_GID))
> > > >      return -EPERM
> > > 
> > > The driver currently does not have access to the callback or the
> > > skbuffer. Sending these details as param to driver won't be right as
> > > drm_ras needs to handle all the netlink buffers.
> > > 
> > > How about using pre_doit & start calls? If driver has a pre callback
> > > , it's the responsibility of the driver to check permissions/any-pre
> > > conditions, else the CAP_NET_ADMIN permission will be checked.
> > > 
> > > @Zack / @Rodrigo thoughts?
> > > @Zack Will this work for your usecase?
> > > 
> > > yaml
> > > +    dump:
> > > +        pre: drm-ras-nl-pre-list-nodes
> > > 
> > > 
> > > drm_ras.c :
> > > 
> > > +       if (node->pre_list_nodes)
> > > +                return node->pre_list_nodes(node);
> > > +
> > > +        return check_permissions(cb->skb);  //Checks creds
> > > 
> > > Thanks
> > > Riana
> > > 
> > 
> > I agree that a pre_doit is probably the best solution for this.
> > 
> > Not entirely sure what a driver specific implementation would look like
> > yet, but I think that as long as the driver callback has a way to access
> > the 'current' task_struct pointer corresponding to the user process then
> > this approach seems like the best option from the netlink side.
> > 
> > Since this is mostly a concern for our specific use case, perhaps we can
> > incorporate this functionality in our change down the road when we
> > expand the interface for telemetry?

Yes, as it can be changed transparently, let's do that...

> 
> 
> Yeah using pre_doit we can allow driver to make decisions based on
> the private data or driver specific permissions. However we will need to
> check the CAP_NET_ADMIN when no driver callback is implemented in the
> netlink layer as a default .
> 
> Thank you, you can incorporate the changes when you add telemetry nodes.
> 
> For now, I will retain the admin-perm in flags.

Cool then, when they come with their case we remove it and force in the
pre_doit as well.

ack..

> 
> I will address the rest of the review comments and send out a new revision
> shortly.
> 
> Thank you
> Riana
> 
> 
> > 
> > Let me know what you think.
> > 
> > Zack
> > 
> > > > 
> > > > or something like that?!
> > > > 
> > > > perhaps drivers could implement some form of cookie or pre-
> > > > authorization with
> > > > ioctls or sysfs, and then store in the priv?
> > > > 
> > > > Thoughts?
> > > > Other options?
> > > > 
> > > > > 
> > > > > I dont see any such permissions checks in your driver
> > > > > implementation which
> > > > > is understandable given that it may not be necessary for
> > > > > your use cases.
> > > > > However, this would be a concern for our driver if we were
> > > > > to adopt this
> > > > > interface.
> > > > 
> > > > yeap, this case was entirely with admin-perm, so not needed at all...
> > > > But I see your point and this is really not giving any flexibility to
> > > > other drivers.
> > > > 
> > 
> > > > > > > 
> > > > > 
> > > > > Thanks,
> > > > > 
> > > > > Zack
> > > > > 
> > > 
> > 
>