If the element exists and no NLM_F_EXCL is specified, do not bump
set->nelems, otherwise we leak one set element slot. This problem
amplifies if the set is full since the abort path always decrements the
counter for the -ENFILE case too, giving one spare extra slot.
Fix this by moving set->nelems update to nft_add_set_elem() after
successful element insertion. Moreover, remove the element if the set is
full so there is no need to rely on the abort path to undo things
anymore.
Fixes: c016c7e45ddf ("netfilter: nf_tables: honor NLM_F_EXCL flag in set element insertion")
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
v2: http://patchwork.ozlabs.org/patch/716751/ attacks the problem from the
wrong angle since this doesn't catch more corner cases that trigger bugs.
This patch obsoletes this previous try.
net/netfilter/nf_tables_api.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index b84c7b25219b..831a9a16f563 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3745,10 +3745,18 @@ static int nft_add_set_elem(struct nft_ctx *ctx, struct nft_set *set,
goto err5;
}
+ if (set->size &&
+ !atomic_add_unless(&set->nelems, 1, set->size + set->ndeact)) {
+ err = -ENFILE;
+ goto err6;
+ }
+
nft_trans_elem(trans) = elem;
list_add_tail(&trans->list, &ctx->net->nft.commit_list);
return 0;
+err6:
+ set->ops->remove(set, &elem);
err5:
kfree(trans);
err4:
@@ -3795,15 +3803,9 @@ static int nf_tables_newsetelem(struct net *net, struct sock *nlsk,
return -EBUSY;
nla_for_each_nested(attr, nla[NFTA_SET_ELEM_LIST_ELEMENTS], rem) {
- if (set->size &&
- !atomic_add_unless(&set->nelems, 1, set->size + set->ndeact))
- return -ENFILE;
-
err = nft_add_set_elem(&ctx, set, attr, nlh->nlmsg_flags);
- if (err < 0) {
- atomic_dec(&set->nelems);
+ if (err < 0)
break;
- }
}
return err;
}
--
2.1.4
--
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