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

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

[Alban Crequy]

From: Alban Crequy <alban@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 <alban@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

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

[Martin Lau]

On Thu, Feb 21, 2019 at 05:39:26PM +0100, Alban Crequy wrote:
> From: Alban Crequy <alban@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
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 <kraig@google.com>

> 
> Signed-off-by: Alban Crequy <alban@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
> 

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

[Alban Crequy]

On Thu, Feb 21, 2019 at 11:24 PM Martin Lau <kafai@fb.com> wrote:
>
> On Thu, Feb 21, 2019 at 05:39:26PM +0100, Alban Crequy wrote:
> > From: Alban Crequy <alban@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
> 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 <kraig@google.com>

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

Cheers,
Alban

> > Signed-off-by: Alban Crequy <alban@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
> >