linux-kernel - Re: [PATCH] bpf: Fix out-of-bounds write in trie_get_next

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Message-ID: <87a5ewiib6.fsf@toke.dk>
Date: Tue, 22 Oct 2024 11:43:41 +0200
From: Toke Høiland-Jørgensen <toke@...nel.org>
To: Byeonguk Jeong <jungbu2855@...il.com>, Daniel Borkmann
 <daniel@...earbox.net>, Yonghong Song <yonghong.song@...ux.dev>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bpf: Fix out-of-bounds write in trie_get_next_key()

Byeonguk Jeong <jungbu2855@...il.com> writes:

> 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.
>
> Fixes: b471f2f1de8b ("bpf: implement MAP_GET_NEXT_KEY command for LPM_TRIE map")
> Signed-off-by: Byeonguk Jeong <jungbu2855@...il.com>

Makes sense!

Reviewed-by: Toke Høiland-Jørgensen <toke@...nel.org>