Re: [PATCH v3 5/5] nouveau/gsp: Cleanup IS_ERR_OR_NULL in nvkm_gsp_rpc_rd()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] A malformed GSP message size causes r535_gsp_msgq_recv() to return NULL, which propagates through nvkm_gsp_rpc_rd() and leads to a NULL pointer dereference in its callers.
--

commit 604de241374540fdccd3d8af5fec3fe8ff826d71
Author: Hongling Zeng <zenghongling@kylinos.cn>

    nouveau/gsp: Cleanup IS_ERR_OR_NULL in nvkm_gsp_rpc_rd()

    This commit cleans up nvkm_gsp_rpc_rd() by replacing IS_ERR_OR_NULL()
    with IS_ERR(). The commit message notes that nvkm_gsp_rpc_push() expects
    a reply under the RECV policy and should return an error pointer rather
    than NULL if the RPC fails.

> diff --git a/drivers/gpu/drm/nouveau/include/nvkm/subdev/gsp.h b/drivers/gpu/drm/nouveau/include/nvkm/subdev/gsp.h
> index 64fed208e4cf8..a061779e0107b 100644
> --- a/drivers/gpu/drm/nouveau/include/nvkm/subdev/gsp.h
> +++ b/drivers/gpu/drm/nouveau/include/nvkm/subdev/gsp.h
> @@ -293,7 +293,7 @@ nvkm_gsp_rpc_rd(struct nvkm_gsp *gsp, u32 fn, u32 argc)
>  {
>  	void *argv = nvkm_gsp_rpc_get(gsp, fn, argc);
>  
> -	if (IS_ERR_OR_NULL(argv))
> +	if (IS_ERR(argv))
>  		return argv;
>  
>  	return nvkm_gsp_rpc_push(gsp, argv, NVKM_GSP_RPC_REPLY_RECV, argc);

[Severity: High]
This is a pre-existing issue, but does nvkm_gsp_rpc_push() strictly return
an error pointer instead of NULL on failure under the RECV policy?

If the GSP firmware returns an RPC message with an invalid length,
r535_gsp_msgq_recv() triggers a WARN_ON and returns NULL:

r535_gsp_msgq_recv() in drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/rpc.c:

	...
	if (WARN_ON(rpc->length > max_rpc_size))
		return NULL;
	...

This NULL propagates up through r535_gsp_msg_recv() and
r535_gsp_rpc_handle_reply() to nvkm_gsp_rpc_push(), which is then returned
directly by nvkm_gsp_rpc_rd() here.

Since callers like r535_gsp_get_static_info() only check IS_ERR(), could this
lead to a NULL pointer dereference?

r535_gsp_get_static_info() in drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/gsp.c:

	...
	rpc = nvkm_gsp_rpc_rd(gsp, NV_VGPU_MSG_FUNCTION_GET_GSP_STATIC_INFO, sizeof(*rpc));
	if (IS_ERR(rpc))
		return PTR_ERR(rpc);

	gsp->internal.client.object.client = &gsp->internal.client;
	gsp->internal.client.object.parent = NULL;
	gsp->internal.client.object.handle = rpc->hInternalClient;
	...

Similarly, does r535_gsp_rpc_rm_ctrl_push() mishandle this NULL?

r535_gsp_rpc_rm_ctrl_push() in drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/ctrl.c:

	...
	repv = nvkm_gsp_rpc_push(gsp, rpc, repc ? NVKM_GSP_RPC_REPLY_RECV :
					   NVKM_GSP_RPC_REPLY_NOWAIT, repc);
	if (IS_ERR_OR_NULL(repv)) {
		*params = NULL;
		return PTR_ERR(repv);
	}
	...

If nvkm_gsp_rpc_push() returns NULL, PTR_ERR(repv) evaluates to 0 (success),
which causes it to return success while passing a NULL pointer back to callers
like r535_gsp_intr_get_table().

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260622021207.14764-1-zenghongling@kylinos.cn?part=5