On Tue, Sep 17, 2019 at 03:48:42PM -0600, Jordan Crouse wrote:
> It is possible for unaware callers of several idr functions to accidentally
> underflow the index by specifying a id that is less than the idr base.
Hi Jordan. Thanks for the patch, but this seems like a distinction
without a difference.
> void *idr_remove(struct idr *idr, unsigned long id)
> {
> + if (id < idr->idr_base)
> + return NULL;
> +
> return radix_tree_delete_item(&idr->idr_rt, id - idr->idr_base, NULL);
If this underflows, we'll try to delete an index which doesn't exist,
which will return NULL.
> void *idr_find(const struct idr *idr, unsigned long id)
> {
> + if (id < idr->idr_base)
> + return NULL;
> +
> return radix_tree_lookup(&idr->idr_rt, id - idr->idr_base);
If this underflows, we'll look up an entry which doesn't exist, which
will return NULL.
> @@ -302,6 +308,9 @@ void *idr_replace(struct idr *idr, void *ptr, unsigned long id)
> void __rcu **slot = NULL;
> void *entry;
>
> + if (id < idr->idr_base)
> + return ERR_PTR(-ENOENT);
> +
> id -= idr->idr_base;
>
> entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot);
... just outside the context is this line:
if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))
return ERR_PTR(-ENOENT);
Looking up an index which doesn't exist gets you a NULL slot, so you get
-ENOENT anyway.
I did think about these possibilities when I was writing the code and
convinced myself I didn't need them. If you have an example of a case
where I got thast wrong, I'd love to see it.
More generally, the IDR is deprecated; I'm trying to convert users to
the XArray. If you're adding a new user, can you use the XArray API
instead?
