[PATCH AUTOSEL 5.0 020/262] netfilter: nf_tables: fix set double-free in abort path

* [PATCH AUTOSEL 5.0 020/262] netfilter: nf_tables: fix set double-free in abort path
       [not found] <20190327180158.10245-1-sashal@kernel.org>
@ 2019-03-27 17:57 ` Sasha Levin
  2019-03-27 17:58 ` [PATCH AUTOSEL 5.0 053/262] netfilter: nf_tables: check the result of dereferencing base_chain->stats Sasha Levin
                   ` (3 subsequent siblings)
  4 siblings, 0 replies; 5+ messages in thread
From: Sasha Levin @ 2019-03-27 17:57 UTC (permalink / raw)
  To: linux-kernel, stable
  Cc: Pablo Neira Ayuso, Sasha Levin, netfilter-devel, coreteam, netdev

From: Pablo Neira Ayuso <pablo@netfilter.org>

[ Upstream commit 40ba1d9b4d19796afc9b7ece872f5f3e8f5e2c13 ]

The abort path can cause a double-free of an anonymous set.
Added-and-to-be-aborted rule looks like this:

udp dport { 137, 138 } drop

The to-be-aborted transaction list looks like this:

newset
newsetelem
newsetelem
rule

This gets walked in reverse order, so first pass disables the rule, the
set elements, then the set.

After synchronize_rcu(), we then destroy those in same order: rule, set
element, set element, newset.

Problem is that the anonymous set has already been bound to the rule, so
the rule (lookup expression destructor) already frees the set, when then
cause use-after-free when trying to delete the elements from this set,
then try to free the set again when handling the newset expression.

Rule releases the bound set in first place from the abort path, this
causes the use-after-free on set element removal when undoing the new
element transactions. To handle this, skip new element transaction if
set is bound from the abort path.

This is still causes the use-after-free on set element removal.  To
handle this, remove transaction from the list when the set is already
bound.

Joint work with Florian Westphal.

Fixes: f6ac85858976 ("netfilter: nf_tables: unbind set in rule from commit path")
Bugzilla: https://bugzilla.netfilter.org/show_bug.cgi?id=1325
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/net/netfilter/nf_tables.h |  6 ++----
 net/netfilter/nf_tables_api.c     | 17 +++++++++++------
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index b4984bbbe157..3d58acf94dd2 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -416,7 +416,8 @@ struct nft_set {
 	unsigned char			*udata;
 	/* runtime data below here */
 	const struct nft_set_ops	*ops ____cacheline_aligned;
-	u16				flags:14,
+	u16				flags:13,
+					bound:1,
 					genmask:2;
 	u8				klen;
 	u8				dlen;
@@ -1329,15 +1330,12 @@ struct nft_trans_rule {
 struct nft_trans_set {
 	struct nft_set			*set;
 	u32				set_id;
-	bool				bound;
 };
 
 #define nft_trans_set(trans)	\
 	(((struct nft_trans_set *)trans->data)->set)
 #define nft_trans_set_id(trans)	\
 	(((struct nft_trans_set *)trans->data)->set_id)
-#define nft_trans_set_bound(trans)	\
-	(((struct nft_trans_set *)trans->data)->bound)
 
 struct nft_trans_chain {
 	bool				update;
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 4893f248dfdc..e1724f9d8b9d 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -127,7 +127,7 @@ static void nft_set_trans_bind(const struct nft_ctx *ctx, struct nft_set *set)
 	list_for_each_entry_reverse(trans, &net->nft.commit_list, list) {
 		if (trans->msg_type == NFT_MSG_NEWSET &&
 		    nft_trans_set(trans) == set) {
-			nft_trans_set_bound(trans) = true;
+			set->bound = true;
 			break;
 		}
 	}
@@ -6617,8 +6617,7 @@ static void nf_tables_abort_release(struct nft_trans *trans)
 		nf_tables_rule_destroy(&trans->ctx, nft_trans_rule(trans));
 		break;
 	case NFT_MSG_NEWSET:
-		if (!nft_trans_set_bound(trans))
-			nft_set_destroy(nft_trans_set(trans));
+		nft_set_destroy(nft_trans_set(trans));
 		break;
 	case NFT_MSG_NEWSETELEM:
 		nft_set_elem_destroy(nft_trans_elem_set(trans),
@@ -6691,8 +6690,11 @@ static int __nf_tables_abort(struct net *net)
 			break;
 		case NFT_MSG_NEWSET:
 			trans->ctx.table->use--;
-			if (!nft_trans_set_bound(trans))
-				list_del_rcu(&nft_trans_set(trans)->list);
+			if (nft_trans_set(trans)->bound) {
+				nft_trans_destroy(trans);
+				break;
+			}
+			list_del_rcu(&nft_trans_set(trans)->list);
 			break;
 		case NFT_MSG_DELSET:
 			trans->ctx.table->use++;
@@ -6700,8 +6702,11 @@ static int __nf_tables_abort(struct net *net)
 			nft_trans_destroy(trans);
 			break;
 		case NFT_MSG_NEWSETELEM:
+			if (nft_trans_elem_set(trans)->bound) {
+				nft_trans_destroy(trans);
+				break;
+			}
 			te = (struct nft_trans_elem *)trans->data;
-
 			te->set->ops->remove(net, te->set, &te->elem);
 			atomic_dec(&te->set->nelems);
 			break;
-- 
2.19.1


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