Re: [PATCH] drm/nouveau/gsp: fix mismatched alloc/free for kvmalloc()

[Timur Tabi <ttabi@nvidia.com>]

On Mon, 2025-08-11 at 17:19 +0800, Qianfeng Rong wrote:
> Replace kfree() with kvfree() for memory allocated by kvmalloc().
> 
> Compile-tested only.
> 
> Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>

Reviewed-by: Timur Tabi <ttabi@nvidia.com>

This does fix a real bug.

However, I think the real problem is that it's really confusing that
r535_gsp_msgq_recv_one_elem(gsp, &info) returns info.gsp_rpc_buf instead of just success/failure. 
r535_gsp_msgq_recv() does this:

	buf = kvmalloc(max_t(u32, rpc->length, expected), GFP_KERNEL);
...
	info.gsp_rpc_buf = buf;
... 
	buf = r535_gsp_msgq_recv_one_elem(gsp, &info);

You wouldn't know it, but this does not change the value of 'buf' unless
r535_gsp_msgq_recv_one_elem() fails.  If it does fail, the code does this:

	if (IS_ERR(buf)) {
		kvfree(info.gsp_rpc_buf);

It would be a lot clearer if we could kvfree(buf) here, but we can't because 'buf' no longer points
to the buffer, even though the buffer still exists.