[PATCH nf] netfilter: nft_set_rbtree: overlap detection with element re-addition after deletion

[PATCH nf] netfilter: nft_set_rbtree: overlap detection with element re-addition after deletion

[Pablo Neira Ayuso]

This patch fixes spurious EEXIST errors.

Extend d2df92e98a34 ("netfilter: nft_set_rbtree: handle element
re-addition after deletion") to deal with elements with same end flags
in the same transation.

Reset the overlap flag as described by 7c84d41416d8 ("netfilter:
nft_set_rbtree: Detect partial overlaps on insertion").

Fixes: 7c84d41416d8 ("netfilter: nft_set_rbtree: Detect partial overlaps on insertion")
Fixes: d2df92e98a34 ("netfilter: nft_set_rbtree: handle element re-addition after deletion")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
This bug is triggered since the new code to online interval automerging
of addition and deletions with an existing kernel set.

https://lore.kernel.org/netfilter-devel/20220412144711.93354-1-pablo@netfilter.org/

 net/netfilter/nft_set_rbtree.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c
index d600a566da32..7325bee7d144 100644
--- a/net/netfilter/nft_set_rbtree.c
+++ b/net/netfilter/nft_set_rbtree.c
@@ -349,7 +349,11 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set,
 				*ext = &rbe->ext;
 				return -EEXIST;
 			} else {
-				p = &parent->rb_left;
+				overlap = false;
+				if (nft_rbtree_interval_end(rbe))
+					p = &parent->rb_left;
+				else
+					p = &parent->rb_right;
 			}
 		}
 
-- 
2.30.2

Re: [PATCH nf] netfilter: nft_set_rbtree: overlap detection with element re-addition after deletion

[Stefano Brivio]

Hi Pablo,

On Mon, 18 Apr 2022 12:21:05 +0200
Pablo Neira Ayuso <pablo@netfilter.org> wrote:

> This patch fixes spurious EEXIST errors.
> 
> Extend d2df92e98a34 ("netfilter: nft_set_rbtree: handle element
> re-addition after deletion") to deal with elements with same end flags
> in the same transation.
> 
> Reset the overlap flag as described by 7c84d41416d8 ("netfilter:
> nft_set_rbtree: Detect partial overlaps on insertion").
> 
> Fixes: 7c84d41416d8 ("netfilter: nft_set_rbtree: Detect partial overlaps on insertion")
> Fixes: d2df92e98a34 ("netfilter: nft_set_rbtree: handle element re-addition after deletion")
> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Sorry for the delay, and thanks for fixing this. I believe this is
correct, but I haven't tested it.

Reviewed-by: Stefano Brivio <sbrivio@redhat.com>

-- 
Stefano