netfilter: nft_rbtree: fix data handling of end interval elements

This patch fixes several things which related to the handling of
end interval elements:

* Chain use underflow with intervals and map: If you add a rule
  using intervals+map that introduces a loop, the error path of the
  rbtree set decrements the chain refcount for each side of the
  interval, leading to a chain use counter underflow.

* Don't copy the data part of the end interval element since, this
  area is uninitialized and this confuses the loop detection code.

* Don't allocate room for the data part of end interval elements
  since this is unused.

So, after this patch the idea is that end interval elements don't
have a data part.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Patrick McHardy <kaber@trash.net>

1 files changed, 11 insertions, 5 deletions

diff --git a/net/netfilter/nft_rbtree.c b/net/netfilter/nft_rbtree.c
index ca0c1b231bfe..e21d69d13506 100644
--- a/net/netfilter/nft_rbtree.c
+++ b/net/netfilter/nft_rbtree.c
@@ -69,8 +69,10 @@ static void nft_rbtree_elem_destroy(const struct nft_set *set,
                                     struct nft_rbtree_elem *rbe)
 {
         nft_data_uninit(&rbe->key, NFT_DATA_VALUE);
-        if (set->flags & NFT_SET_MAP)
+        if (set->flags & NFT_SET_MAP &&
+            !(rbe->flags & NFT_SET_ELEM_INTERVAL_END))
                 nft_data_uninit(rbe->data, set->dtype);
+
         kfree(rbe);
 }
 
@@ -108,7 +110,8 @@ static int nft_rbtree_insert(const struct nft_set *set,
         int err;
 
         size = sizeof(*rbe);
-        if (set->flags & NFT_SET_MAP)
+        if (set->flags & NFT_SET_MAP &&
+            !(elem->flags & NFT_SET_ELEM_INTERVAL_END))
                 size += sizeof(rbe->data[0]);
 
         rbe = kzalloc(size, GFP_KERNEL);
@@ -117,7 +120,8 @@ static int nft_rbtree_insert(const struct nft_set *set,
 
         rbe->flags = elem->flags;
         nft_data_copy(&rbe->key, &elem->key);
-        if (set->flags & NFT_SET_MAP)
+        if (set->flags & NFT_SET_MAP &&
+            !(rbe->flags & NFT_SET_ELEM_INTERVAL_END))
                 nft_data_copy(rbe->data, &elem->data);
 
         err = __nft_rbtree_insert(set, rbe);
@@ -153,7 +157,8 @@ static int nft_rbtree_get(const struct nft_set *set, struct nft_set_elem *elem)
                         parent = parent->rb_right;
                 else {
                         elem->cookie = rbe;
-                        if (set->flags & NFT_SET_MAP)
+                        if (set->flags & NFT_SET_MAP &&
+                            !(rbe->flags & NFT_SET_ELEM_INTERVAL_END))
                                 nft_data_copy(&elem->data, rbe->data);
                         elem->flags = rbe->flags;
                         return 0;
@@ -177,7 +182,8 @@ static void nft_rbtree_walk(const struct nft_ctx *ctx,
 
                 rbe = rb_entry(node, struct nft_rbtree_elem, node);
                 nft_data_copy(&elem.key, &rbe->key);
-                if (set->flags & NFT_SET_MAP)
+                if (set->flags & NFT_SET_MAP &&
+                    !(rbe->flags & NFT_SET_ELEM_INTERVAL_END))
                         nft_data_copy(&elem.data, rbe->data);
                 elem.flags = rbe->flags;