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From:   Martin Lau <kafai@fb.com>
To:     Alban Crequy <alban.crequy@gmail.com>
CC:     "ast@kernel.org" <ast@kernel.org>,
        "daniel@iogearbox.net" <daniel@iogearbox.net>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "alban@kinvolk.io" <alban@kinvolk.io>,
        "iago@kinvolk.io" <iago@kinvolk.io>,
        Craig Gallek <kraig@google.com>
Subject: Re: [PATCH bpf-next v1] bpf, lpm: fix lookup bug in map_delete_elem
Thread-Topic: [PATCH bpf-next v1] bpf, lpm: fix lookup bug in map_delete_elem
Thread-Index: AQHUygQlhnaFWKZBg0GeAn9mNGwt5KXq1DQA
Date:   Thu, 21 Feb 2019 22:23:57 +0000
Message-ID: <20190221222350.6u2jbtias2c3mgyy@kafai-mbp.dhcp.thefacebook.com>
References: <20190221163926.15221-1-alban@kinvolk.io>
In-Reply-To: <20190221163926.15221-1-alban@kinvolk.io>
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On Thu, Feb 21, 2019 at 05:39:26PM +0100, Alban Crequy wrote:
> From: Alban Crequy <alban@kinvolk.io>
>=20
> 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.
>=20
> Reproducer:
>=20
> $ sudo bpftool map create /sys/fs/bpf/mylpm type lpm_trie key 8 value 1 e=
ntries 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
The change makes sense to me.  Can you add this reproducer to
tools/testing/selftests/bpf/test_lpm_map.c?

Bug fix should be for the "bpf" tree instead of "bpf-next"
Fixes tag is also required, like

Fixes: e454cf595853 ("bpf: Implement map_delete_elem for BPF_MAP_TYPE_LPM_T=
RIE")
Cc: Craig Gallek <kraig@google.com>

>=20
> Signed-off-by: Alban Crequy <alban@kinvolk.io>
> ---
>  kernel/bpf/lpm_trie.c | 1 +
>  1 file changed, 1 insertion(+)
>=20
> 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)
>  	}
> =20
>  	if (!node || node->prefixlen !=3D key->prefixlen ||
> +	    node->prefixlen !=3D matchlen ||
>  	    (node->flags & LPM_TREE_NODE_FLAG_IM)) {
>  		ret =3D -ENOENT;
>  		goto out;
> --=20
> 2.20.1
>=20