Re: [PATCH] bpf: Fix out-of-bounds write in trie_get_next_key()

[Alexei Starovoitov]

On Mon, Oct 21, 2024 at 6:49 PM Byeonguk Jeong <jungbu2855@xxxxxxxxx> wrote:
>
> trie_get_next_key() allocates a node stack with size trie->max_prefixlen,
> while it writes (trie->max_prefixlen + 1) nodes to the stack when it has
> full paths from the root to leaves. For example, consider a trie with
> max_prefixlen is 8, and the nodes with key 0x00/0, 0x00/1, 0x00/2, ...
> 0x00/8 inserted. Subsequent calls to trie_get_next_key with _key with
> .prefixlen = 8 make 9 nodes be written on the node stack with size 8.

Hmm. It sounds possible, but pls demonstrate it with a selftest.
With the amount of fuzzing I'm surprised it was not discovered earlier.

pw-bot: cr