From dc843ed97ddb70df2b4c18777123bf05ba044599 Mon Sep 17 00:00:00 2001 From: Florian Lehner Date: Sun, 5 Nov 2023 09:58:01 +0100 Subject: [PATCH] bpf, lpm: Fix check prefixlen before walking trie [ Upstream commit 9b75dbeb36fcd9fc7ed51d370310d0518a387769 ] When looking up an element in LPM trie, the condition 'matchlen == trie->max_prefixlen' will never return true, if key->prefixlen is larger than trie->max_prefixlen. Consequently all elements in the LPM trie will be visited and no element is returned in the end. To resolve this, check key->prefixlen first before walking the LPM trie. Fixes: b95a5c4db09b ("bpf: add a longest prefix match trie map implementation") Signed-off-by: Florian Lehner Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20231105085801.3742-1-dev@der-flo.net Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- kernel/bpf/lpm_trie.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c index 56e6c75d354d..d78c1afe1273 100644 --- a/kernel/bpf/lpm_trie.c +++ b/kernel/bpf/lpm_trie.c @@ -230,6 +230,9 @@ static void *trie_lookup_elem(struct bpf_map *map, void *_key) struct lpm_trie_node *node, *found = NULL; struct bpf_lpm_trie_key *key = _key; + if (key->prefixlen > trie->max_prefixlen) + return NULL; + /* Start walking the trie from the root node ... */ for (node = rcu_dereference(trie->root); node;) {