Commit 7c0cdf0b authored Feb 22, 2019 by Alban Crequy Committed by Daniel Borkmann Feb 22, 2019

bpf, lpm: fix lookup bug in map_delete_elem



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

A similar reproducer is added in the selftests.

Without the patch:

$ sudo ./tools/testing/selftests/bpf/test_lpm_map
test_lpm_map: test_lpm_map.c:485: test_lpm_delete: Assertion `bpf_map_delete_elem(map_fd, key) == -1 && errno == ENOENT' failed.
Aborted

With the patch: test_lpm_map runs without errors.

Fixes: e454cf59 ("bpf: Implement map_delete_elem for BPF_MAP_TYPE_LPM_TRIE")
Cc: Craig Gallek <kraig@google.com>
Signed-off-by: Alban Crequy <alban@kinvolk.io>
Acked-by: Craig Gallek <kraig@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent 11fe9262

kernel/bpf/lpm_trie.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -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;

tools/testing/selftests/bpf/test_lpm_map.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -474,6 +474,16 @@ static void test_lpm_delete(void)
		assert(bpf_map_lookup_elem(map_fd, key, &value) == -1 &&
		errno == ENOENT);

		key->prefixlen = 30; // unused prefix so far
		inet_pton(AF_INET, "192.255.0.0", key->data);
		assert(bpf_map_delete_elem(map_fd, key) == -1 &&
		errno == ENOENT);

		key->prefixlen = 16; // same prefix as the root node
		inet_pton(AF_INET, "192.255.0.0", key->data);
		assert(bpf_map_delete_elem(map_fd, key) == -1 &&
		errno == ENOENT);

		/* assert initial lookup */
		key->prefixlen = 32;
		inet_pton(AF_INET, "192.168.0.1", key->data);

Admin message