Re: [PATCH bpf v2] bpf, lpm: fix lookup bug in map_delete_elem

[Craig Gallek]

On Fri, Feb 22, 2019 at 8:19 AM Alban Crequy <alban.crequy@xxxxxxxxx> wrote:
>
> From: Alban Crequy <alban@xxxxxxxxxx>
>
> 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: e454cf595853 ("bpf: Implement map_delete_elem for BPF_MAP_TYPE_LPM_TRIE")
> Cc: Craig Gallek <kraig@xxxxxxxxxx>
> Signed-off-by: Alban Crequy <alban@xxxxxxxxxx>
>
> ---
Acked-by: Craig Gallek <kraig@xxxxxxxxxx>

Good catch, thanks for the fix!