netfilter: nf_tables: fix *leak* when expr clone fail

When nft_expr_clone failed, a series of problems will happen:

1. module refcnt will leak, we call __module_get at the beginning but
   we forget to put it back if ops->clone returns fail
2. memory will be leaked, if clone fail, we just return NULL and forget
   to free the alloced element
3. set->nelems will become incorrect when set->size is specified. If
   clone fail, we should decrease the set->nelems

Now this patch fixes these problems. And fortunately, clone fail will
only happen on counter expression when memory is exhausted.

Fixes: 086f332167d6 ("netfilter: nf_tables: add clone interface to expression operations")
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

5 files changed, 23 insertions, 16 deletions

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 5031e072567b..741dcded5b4f 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -542,7 +542,8 @@ void *nft_set_elem_init(const struct nft_set *set,
                         const struct nft_set_ext_tmpl *tmpl,
                         const u32 *key, const u32 *data,
                         u64 timeout, gfp_t gfp);
-void nft_set_elem_destroy(const struct nft_set *set, void *elem);
+void nft_set_elem_destroy(const struct nft_set *set, void *elem,
+                          bool destroy_expr);
 
 /**
  *      struct nft_set_gc_batch_head - nf_tables set garbage collection batch
@@ -693,7 +694,6 @@ static inline int nft_expr_clone(struct nft_expr *dst, struct nft_expr *src)
 {
         int err;
 
-        __module_get(src->ops->type->owner);
         if (src->ops->clone) {
                 dst->ops = src->ops;
                 err = src->ops->clone(dst, src);
@@ -702,6 +702,8 @@ static inline int nft_expr_clone(struct nft_expr *dst, struct nft_expr *src)
         } else {
                 memcpy(dst, src, src->ops->size);
         }
+
+        __module_get(src->ops->type->owner);
         return 0;
 }
 
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 24db22257586..86e48aeb20be 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3452,14 +3452,15 @@ void *nft_set_elem_init(const struct nft_set *set,
         return elem;
 }
 
-void nft_set_elem_destroy(const struct nft_set *set, void *elem)
+void nft_set_elem_destroy(const struct nft_set *set, void *elem,
+                          bool destroy_expr)
 {
         struct nft_set_ext *ext = nft_set_elem_ext(set, elem);
 
         nft_data_uninit(nft_set_ext_key(ext), NFT_DATA_VALUE);
         if (nft_set_ext_exists(ext, NFT_SET_EXT_DATA))
                 nft_data_uninit(nft_set_ext_data(ext), set->dtype);
-        if (nft_set_ext_exists(ext, NFT_SET_EXT_EXPR))
+        if (destroy_expr && nft_set_ext_exists(ext, NFT_SET_EXT_EXPR))
                 nf_tables_expr_destroy(NULL, nft_set_ext_expr(ext));
 
         kfree(elem);
@@ -3812,7 +3813,7 @@ void nft_set_gc_batch_release(struct rcu_head *rcu)
 
         gcb = container_of(rcu, struct nft_set_gc_batch, head.rcu);
         for (i = 0; i < gcb->head.cnt; i++)
-                nft_set_elem_destroy(gcb->head.set, gcb->elems[i]);
+                nft_set_elem_destroy(gcb->head.set, gcb->elems[i], true);
         kfree(gcb);
 }
 EXPORT_SYMBOL_GPL(nft_set_gc_batch_release);
@@ -4030,7 +4031,7 @@ static void nf_tables_commit_release(struct nft_trans *trans)
                 break;
         case NFT_MSG_DELSETELEM:
                 nft_set_elem_destroy(nft_trans_elem_set(trans),
-                                     nft_trans_elem(trans).priv);
+                                     nft_trans_elem(trans).priv, true);
                 break;
         }
         kfree(trans);
@@ -4171,7 +4172,7 @@ static void nf_tables_abort_release(struct nft_trans *trans)
                 break;
         case NFT_MSG_NEWSETELEM:
                 nft_set_elem_destroy(nft_trans_elem_set(trans),
-                                     nft_trans_elem(trans).priv);
+                                     nft_trans_elem(trans).priv, true);
                 break;
         }
         kfree(trans);
diff --git a/net/netfilter/nft_dynset.c b/net/netfilter/nft_dynset.c
index bfdb689664b0..31ca94793aa9 100644
--- a/net/netfilter/nft_dynset.c
+++ b/net/netfilter/nft_dynset.c
@@ -44,18 +44,22 @@ static void *nft_dynset_new(struct nft_set *set, const struct nft_expr *expr,
                                  &regs->data[priv->sreg_key],
                                  &regs->data[priv->sreg_data],
                                  timeout, GFP_ATOMIC);
-        if (elem == NULL) {
-                if (set->size)
-                        atomic_dec(&set->nelems);
-                return NULL;
-        }
+        if (elem == NULL)
+                goto err1;
 
         ext = nft_set_elem_ext(set, elem);
         if (priv->expr != NULL &&
             nft_expr_clone(nft_set_ext_expr(ext), priv->expr) < 0)
-                return NULL;
+                goto err2;
 
         return elem;
+
+err2:
+        nft_set_elem_destroy(set, elem, false);
+err1:
+        if (set->size)
+                atomic_dec(&set->nelems);
+        return NULL;
 }
 
 static void nft_dynset_eval(const struct nft_expr *expr,
diff --git a/net/netfilter/nft_set_hash.c b/net/netfilter/nft_set_hash.c
index 3794cb2fc788..88d9fc8343e7 100644
--- a/net/netfilter/nft_set_hash.c
+++ b/net/netfilter/nft_set_hash.c
@@ -120,7 +120,7 @@ out:
         return true;
 
 err2:
-        nft_set_elem_destroy(set, he);
+        nft_set_elem_destroy(set, he, true);
 err1:
         return false;
 }
@@ -332,7 +332,7 @@ static int nft_hash_init(const struct nft_set *set,
 
 static void nft_hash_elem_destroy(void *ptr, void *arg)
 {
-        nft_set_elem_destroy((const struct nft_set *)arg, ptr);
+        nft_set_elem_destroy((const struct nft_set *)arg, ptr, true);
 }
 
 static void nft_hash_destroy(const struct nft_set *set)
diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c
index 38b5bda242f8..36493a7cae88 100644
--- a/net/netfilter/nft_set_rbtree.c
+++ b/net/netfilter/nft_set_rbtree.c
@@ -266,7 +266,7 @@ static void nft_rbtree_destroy(const struct nft_set *set)
         while ((node = priv->root.rb_node) != NULL) {
                 rb_erase(node, &priv->root);
                 rbe = rb_entry(node, struct nft_rbtree_elem, node);
-                nft_set_elem_destroy(set, rbe);
+                nft_set_elem_destroy(set, rbe, true);
         }
 }