netdev - [PATCH net 3/3] netfilter: nf_tables: incorrect error path handling with NFT_MSG

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Message-Id: <20230608195706.4429-4-pablo@netfilter.org>
Date: Thu,  8 Jun 2023 21:57:06 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net,
	netdev@...r.kernel.org,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com
Subject: [PATCH net 3/3] netfilter: nf_tables: incorrect error path handling with NFT_MSG_NEWRULE

In case of error when adding a new rule that refers to an anonymous set,
deactivate expressions via NFT_TRANS_PREPARE state, not NFT_TRANS_RELEASE.
Thus, the lookup expression marks anonymous sets as inactive in the next
generation to ensure it is not reachable in this transaction anymore and
decrement the set refcount as introduced by c1592a89942e ("netfilter:
nf_tables: deactivate anonymous set from preparation phase"). The abort
step takes care of undoing the anonymous set.

This is also consistent with rule deletion, where NFT_TRANS_PREPARE is
used. Note that this error path is exercised in the preparation step of
the commit protocol. This patch replaces nf_tables_rule_release() by the
deactivate and destroy calls, this time with NFT_TRANS_PREPARE.

Due to this incorrect error handling, it is possible to access a
dangling pointer to the anonymous set that remains in the transaction
list.

[1009.379054] BUG: KASAN: use-after-free in nft_set_lookup_global+0x147/0x1a0 [nf_tables]
[1009.379106] Read of size 8 at addr ffff88816c4c8020 by task nft-rule-add/137110
[1009.379116] CPU: 7 PID: 137110 Comm: nft-rule-add Not tainted 6.4.0-rc4+ #256
[1009.379128] Call Trace:
[1009.379132]  <TASK>
[1009.379135]  dump_stack_lvl+0x33/0x50
[1009.379146]  ? nft_set_lookup_global+0x147/0x1a0 [nf_tables]
[1009.379191]  print_address_description.constprop.0+0x27/0x300
[1009.379201]  kasan_report+0x107/0x120
[1009.379210]  ? nft_set_lookup_global+0x147/0x1a0 [nf_tables]
[1009.379255]  nft_set_lookup_global+0x147/0x1a0 [nf_tables]
[1009.379302]  nft_lookup_init+0xa5/0x270 [nf_tables]
[1009.379350]  nf_tables_newrule+0x698/0xe50 [nf_tables]
[1009.379397]  ? nf_tables_rule_release+0xe0/0xe0 [nf_tables]
[1009.379441]  ? kasan_unpoison+0x23/0x50
[1009.379450]  nfnetlink_rcv_batch+0x97c/0xd90 [nfnetlink]
[1009.379470]  ? nfnetlink_rcv_msg+0x480/0x480 [nfnetlink]
[1009.379485]  ? __alloc_skb+0xb8/0x1e0
[1009.379493]  ? __alloc_skb+0xb8/0x1e0
[1009.379502]  ? entry_SYSCALL_64_after_hwframe+0x46/0xb0
[1009.379509]  ? unwind_get_return_address+0x2a/0x40
[1009.379517]  ? write_profile+0xc0/0xc0
[1009.379524]  ? avc_lookup+0x8f/0xc0
[1009.379532]  ? __rcu_read_unlock+0x43/0x60

Fixes: 958bee14d071 ("netfilter: nf_tables: use new transaction infrastructure to handle sets")
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_tables_api.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 3bb0800b3849..69bceefaa5c8 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3844,7 +3844,8 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
 	if (flow)
 		nft_flow_rule_destroy(flow);
 err_release_rule:
-	nf_tables_rule_release(&ctx, rule);
+	nft_rule_expr_deactivate(&ctx, rule, NFT_TRANS_PREPARE);
+	nf_tables_rule_destroy(&ctx, rule);
 err_release_expr:
 	for (i = 0; i < n; i++) {
 		if (expr_info[i].ops) {
-- 
2.30.2