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bpf, lpm: Fix check prefixlen before walking trie

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[ 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 <dev@der-flo.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20231105085801.3742-1-dev@der-flo.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Florian Lehner 2023-11-05 09:58:01 +01:00 committed by Ksawlii
parent 782668fb75
commit 735ab51053
1 changed files with 3 additions and 0 deletions
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3
kernel/bpf/lpm_trie.c
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@ -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;) {