[PATCH bpf-next v1] bpf, lpm: fix lookup bug in map_delete_elem

[Alban Crequy]

From: Alban Crequy <al...@kinvolk.io>

trie_delete_elem() was deleting an entry even though it was not matching
if the prefixlen was correct. This patch adds a check on matchlen.

Reproducer:

$ sudo bpftool map create /sys/fs/bpf/mylpm type lpm_trie key 8 value 1 entries 
128 name mylpm flags 1
$ sudo bpftool map update pinned /sys/fs/bpf/mylpm key hex 10 00 00 00 aa bb cc 
dd value hex 01
$ sudo bpftool map dump pinned /sys/fs/bpf/mylpm
key: 10 00 00 00 aa bb cc dd  value: 01
Found 1 element
$ sudo bpftool map delete pinned /sys/fs/bpf/mylpm key hex 10 00 00 00 ff ff ff 
ff
$ echo $?
0
$ sudo bpftool map dump pinned /sys/fs/bpf/mylpm
Found 0 elements

Signed-off-by: Alban Crequy <al...@kinvolk.io>
---
 kernel/bpf/lpm_trie.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index abf1002080df..93a5cbbde421 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -471,6 +471,7 @@ static int trie_delete_elem(struct bpf_map *map, void *_key)
        }
 
        if (!node || node->prefixlen != key->prefixlen ||
+           node->prefixlen != matchlen ||
            (node->flags & LPM_TREE_NODE_FLAG_IM)) {
                ret = -ENOENT;
                goto out;
-- 
2.20.1