Re: [PATCH v5 27/45] vmw_balloon: dynamically allocate the vmw-balloon shrinker

[Nadav Amit]

> On Aug 23, 2023, at 8:42 PM, Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> wrote:
> 
> In preparation for implementing lockless slab shrink, use new APIs to
> dynamically allocate the vmw-balloon shrinker, so that it can be freed
> asynchronously via RCU. Then it doesn't need to wait for RCU read-side
> critical section when releasing the struct vmballoon.
> 
> And we can simply exit vmballoon_init() when registering the shrinker
> fails. So the shrinker_registered indication is redundant, just remove it.

...

Ugh. We should have already moved to OOM notifier instead...

> static void vmballoon_unregister_shrinker(struct vmballoon *b)
> {
> -	if (b->shrinker_registered)
> -		unregister_shrinker(&b->shrinker);
> -	b->shrinker_registered = false;
> +	shrinker_free(b->shrinker);
> }

If the patch goes through another iteration, please add:

	b->shrinker = NULL;

Not that this is a real issue, but I prefer it so in order to more easily
identify UAF if the function is called elsewhere.

Otherwise, LGTM. Thanks.