netfilter: nf_tables: prepare set element accounting for async updates
Use atomic operations for the element count to avoid races with async
updates.
To properly handle the transactional semantics during netlink updates,
deleted but not yet committed elements are accounted for seperately and
are treated as being already removed. This means for the duration of
a netlink transaction, the limit might be exceeded by the amount of
elements deleted. Set implementations must be prepared to handle this.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 0dab872..27d1bf5 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3238,9 +3238,6 @@
u32 flags;
int err;
- if (set->size && set->nelems == set->size)
- return -ENFILE;
-
err = nla_parse_nested(nla, NFTA_SET_ELEM_MAX, attr,
nft_set_elem_policy);
if (err < 0)
@@ -3391,11 +3388,15 @@
return -EBUSY;
nla_for_each_nested(attr, nla[NFTA_SET_ELEM_LIST_ELEMENTS], rem) {
- err = nft_add_set_elem(&ctx, set, attr);
- if (err < 0)
- break;
+ if (set->size &&
+ !atomic_add_unless(&set->nelems, 1, set->size + set->ndeact))
+ return -ENFILE;
- set->nelems++;
+ err = nft_add_set_elem(&ctx, set, attr);
+ if (err < 0) {
+ atomic_dec(&set->nelems);
+ break;
+ }
}
return err;
}
@@ -3477,7 +3478,7 @@
if (err < 0)
break;
- set->nelems--;
+ set->ndeact++;
}
return err;
}
@@ -3810,6 +3811,8 @@
&te->elem,
NFT_MSG_DELSETELEM, 0);
te->set->ops->remove(te->set, &te->elem);
+ atomic_dec(&te->set->nelems);
+ te->set->ndeact--;
break;
}
}
@@ -3913,16 +3916,16 @@
nft_trans_destroy(trans);
break;
case NFT_MSG_NEWSETELEM:
- nft_trans_elem_set(trans)->nelems--;
te = (struct nft_trans_elem *)trans->data;
te->set->ops->remove(te->set, &te->elem);
+ atomic_dec(&te->set->nelems);
break;
case NFT_MSG_DELSETELEM:
te = (struct nft_trans_elem *)trans->data;
- nft_trans_elem_set(trans)->nelems++;
te->set->ops->activate(te->set, &te->elem);
+ te->set->ndeact--;
nft_trans_destroy(trans);
break;