[PATCH nft] segtree: bogus range via get set element on existing elements

[Pablo Neira Ayuso]

 table ip x {
        set y {
                type inet_service
                flags interval
                elements = { 10, 20-30, 40, 50-60 }
        }
 }

 # nft get element x y { 20-40 }
 table ip x {
        set y {
                type inet_service
                flags interval
                elements = { 20-40 }
        }
 }

20 and 40 exist in the tree, but they are part of different ranges.
This patch adds a new get_set_decompose() function to validate that the
left and the right side of the range.

Reported-by: Phil Sutter <p...@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
---
 include/expression.h |  2 +-
 src/netlink.c        |  5 +++--
 src/segtree.c        | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/include/expression.h b/include/expression.h
index fb52abfea76e..d6977c3ae62e 100644
--- a/include/expression.h
+++ b/include/expression.h
@@ -453,7 +453,7 @@ extern void interval_map_decompose(struct expr *set);
 extern struct expr *get_set_intervals(const struct set *set,
                                      const struct expr *init);
 struct table;
-extern void get_set_decompose(struct table *table, struct set *set);
+extern int get_set_decompose(struct table *table, struct set *set);
 
 extern struct expr *mapping_expr_alloc(const struct location *loc,
                                       struct expr *from, struct expr *to);
diff --git a/src/netlink.c b/src/netlink.c
index f795d984084b..7c3082bb4dc5 100644
--- a/src/netlink.c
+++ b/src/netlink.c
@@ -1361,8 +1361,9 @@ int netlink_get_setelem(struct netlink_ctx *ctx, const 
struct handle *h,
        nftnl_set_free(nls_out);
        ctx->set = NULL;
 
-       if (set->flags & NFT_SET_INTERVAL)
-               get_set_decompose(table, set);
+       if (set->flags & NFT_SET_INTERVAL &&
+           get_set_decompose(table, set) < 0)
+               return -1;
 
        return 0;
 }
diff --git a/src/segtree.c b/src/segtree.c
index 8a8aa71e8a6e..0e40635a592d 100644
--- a/src/segtree.c
+++ b/src/segtree.c
@@ -641,6 +641,43 @@ struct expr *get_set_intervals(const struct set *set, 
const struct expr *init)
        return new_init;
 }
 
+static struct expr *get_set_interval_find(const struct table *table,
+                                         const char *set_name,
+                                         struct expr *left,
+                                         struct expr *right)
+{
+       struct expr *range = NULL;
+       struct set *set;
+       mpz_t low, high;
+       struct expr *i;
+
+       set = set_lookup(table, set_name);
+       mpz_init2(low, set->key->len);
+       mpz_init2(high, set->key->len);
+
+       list_for_each_entry(i, &set->init->expressions, list) {
+               switch (i->key->ops->type) {
+               case EXPR_RANGE:
+                       range_expr_value_low(low, i);
+                       range_expr_value_high(high, i);
+                       if (mpz_cmp(left->key->value, low) >= 0 &&
+                           mpz_cmp(right->key->value, high) <= 0)
+                               range = range_expr_alloc(&internal_location,
+                                                        expr_clone(left->key),
+                                                        
expr_clone(right->key));
+                               break;
+                       break;
+               default:
+                       break;
+               }
+       }
+
+       mpz_clear(low);
+       mpz_clear(high);
+
+       return range;
+}
+
 static struct expr *get_set_interval_end(const struct table *table,
                                         const char *set_name,
                                         struct expr *left)
@@ -675,7 +712,7 @@ static struct expr *get_set_interval_end(const struct table 
*table,
        return left;
 }
 
-void get_set_decompose(struct table *table, struct set *set)
+int get_set_decompose(struct table *table, struct set *set)
 {
        struct expr *i, *next, *new;
        struct expr *left = NULL;
@@ -688,7 +725,13 @@ void get_set_decompose(struct table *table, struct set 
*set)
                        list_del(&left->list);
                        list_del(&i->list);
                        mpz_sub_ui(i->key->value, i->key->value, 1);
-                       new = range_expr_alloc(&internal_location, left, i);
+                       new = get_set_interval_find(table, set->handle.set.name,
+                                                   left, i);
+                       if (!new) {
+                               errno = ENOENT;
+                               return -1;
+                       }
+
                        compound_expr_add(new_init, new);
                        left = NULL;
                } else {
@@ -707,6 +750,8 @@ void get_set_decompose(struct table *table, struct set *set)
        }
 
        set->init = new_init;
+
+       return 0;
 }
 
 static bool range_is_prefix(const mpz_t range)
-- 
2.11.0