2019-02-21 16:40:47

by Alban Crequy

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

From: Alban Crequy <[email protected]>

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 <[email protected]>
---
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

2019-02-21 22:26:40

by Martin KaFai Lau

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

On Thu, Feb 21, 2019 at 05:39:26PM +0100, Alban Crequy wrote:
> From: Alban Crequy <[email protected]>
>
> 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
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_TRIE")
Cc: Craig Gallek <[email protected]>

>
> Signed-off-by: Alban Crequy <[email protected]>
> ---
> 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
>

2019-02-22 13:16:34

by Alban Crequy

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

On Thu, Feb 21, 2019 at 11:24 PM Martin Lau <[email protected]> wrote:
>
> On Thu, Feb 21, 2019 at 05:39:26PM +0100, Alban Crequy wrote:
> > From: Alban Crequy <[email protected]>
> >
> > 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
> 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_TRIE")
> Cc: Craig Gallek <[email protected]>

Thanks! I'll send a v2 shortly with the selftest and the tags, based
on "bpf" tree.

Cheers,
Alban

> > Signed-off-by: Alban Crequy <[email protected]>
> > ---
> > 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
> >