4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Florian Lehner <dev@xxxxxxxxxxx>
[ 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@xxxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20231105085801.3742-1-dev@xxxxxxxxxxx
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 1a8b208f6c55..fcd3a15add41 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -194,6 +194,9 @@ 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;) {
--
2.43.0
