5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hou Tao <houtao1@xxxxxxxxxx> [ Upstream commit 27abc7b3fa2e09bbe41e2924d328121546865eda ] trie_get_next_key() uses node->prefixlen == key->prefixlen to identify an exact match, However, it is incorrect because when the target key doesn't fully match the found node (e.g., node->prefixlen != matchlen), these two nodes may also have the same prefixlen. It will return expected result when the passed key exist in the trie. However when a recently-deleted key or nonexistent key is passed to trie_get_next_key(), it may skip keys and return incorrect result. Fix it by using node->prefixlen == matchlen to identify exact matches. When the condition is true after the search, it also implies node->prefixlen equals key->prefixlen, otherwise, the search would return NULL instead. Fixes: b471f2f1de8b ("bpf: implement MAP_GET_NEXT_KEY command for LPM_TRIE map") Reviewed-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx> Link: https://lore.kernel.org/r/20241206110622.1161752-6-houtao@xxxxxxxxxxxxxxx Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- kernel/bpf/lpm_trie.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c index 1f92d531b4466..f726ceb8d7e96 100644 --- a/kernel/bpf/lpm_trie.c +++ b/kernel/bpf/lpm_trie.c @@ -655,7 +655,7 @@ static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key) struct lpm_trie_node **node_stack = NULL; int err = 0, stack_ptr = -1; unsigned int next_bit; - size_t matchlen; + size_t matchlen = 0; /* The get_next_key follows postorder. For the 4 node example in * the top of this file, the trie_get_next_key() returns the following @@ -694,7 +694,7 @@ static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key) next_bit = extract_bit(key->data, node->prefixlen); node = rcu_dereference(node->child[next_bit]); } - if (!node || node->prefixlen != key->prefixlen || + if (!node || node->prefixlen != matchlen || (node->flags & LPM_TREE_NODE_FLAG_IM)) goto find_leftmost; -- 2.43.0