This is a note to let you know that I've just added the patch titled
bpf, lpm: Fix check prefixlen before walking trie
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-lpm-fix-check-prefixlen-before-walking-trie.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6a740518d24afc198ca65d22632deea277ca60a3
Author: Florian Lehner <dev@xxxxxxxxxxx>
Date: Sun Nov 5 09:58:01 2023 +0100
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 <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>
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;) {
