[PATCH nf 0/2] netfilter: nf_tables: fix nf_trace related crash

[PATCH nf 0/2] netfilter: nf_tables: fix nf_trace related crash

[Florian Westphal]

The commit e34b9ed96ce3 ("netfilter: nf_tables: avoid skb access on nf_stolen")
is broken, it adds read-access to a structure that might contain
garbage.

Fix this and extend the existing nft_trans_stress.sh script to
cover this.

Florian Westphal (2):
  netfilter: nf_tables: fix crash when nf_trace is enabled
  selftests: netfilter: add test case for nf trace infrastructure

 net/netfilter/nf_tables_core.c                | 21 +++--
 .../selftests/netfilter/nft_trans_stress.sh   | 78 ++++++++++++++++++-
 2 files changed, 86 insertions(+), 13 deletions(-)
-- 
2.35.1

[PATCH nf 1/2] netfilter: nf_tables: fix crash when nf_trace is enabled

[Florian Westphal]

nft_traceinfo is not initialized in info->trace is 0, so unconditional
access to info->pkt (or any other field except ->trace) is illegal.

Pass nft_pktinfo directly to avoid this.

Fixes: e34b9ed96ce3 ("netfilter: nf_tables: avoid skb access on nf_stolen")
Reported-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_tables_core.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/net/netfilter/nf_tables_core.c b/net/netfilter/nf_tables_core.c
index 3ddce24ac76d..cee3e4e905ec 100644
--- a/net/netfilter/nf_tables_core.c
+++ b/net/netfilter/nf_tables_core.c
@@ -34,25 +34,23 @@ static noinline void __nft_trace_packet(struct nft_traceinfo *info,
 	nft_trace_notify(info);
 }
 
-static inline void nft_trace_packet(struct nft_traceinfo *info,
+static inline void nft_trace_packet(const struct nft_pktinfo *pkt,
+				    struct nft_traceinfo *info,
 				    const struct nft_chain *chain,
 				    const struct nft_rule_dp *rule,
 				    enum nft_trace_types type)
 {
 	if (static_branch_unlikely(&nft_trace_enabled)) {
-		const struct nft_pktinfo *pkt = info->pkt;
-
 		info->nf_trace = pkt->skb->nf_trace;
 		info->rule = rule;
 		__nft_trace_packet(info, chain, type);
 	}
 }
 
-static inline void nft_trace_copy_nftrace(struct nft_traceinfo *info)
+static inline void nft_trace_copy_nftrace(const struct nft_pktinfo *pkt,
+					  struct nft_traceinfo *info)
 {
 	if (static_branch_unlikely(&nft_trace_enabled)) {
-		const struct nft_pktinfo *pkt = info->pkt;
-
 		if (info->trace)
 			info->nf_trace = pkt->skb->nf_trace;
 	}
@@ -96,7 +94,6 @@ static noinline void __nft_trace_verdict(struct nft_traceinfo *info,
 					 const struct nft_chain *chain,
 					 const struct nft_regs *regs)
 {
-	const struct nft_pktinfo *pkt = info->pkt;
 	enum nft_trace_types type;
 
 	switch (regs->verdict.code) {
@@ -110,7 +107,9 @@ static noinline void __nft_trace_verdict(struct nft_traceinfo *info,
 		break;
 	default:
 		type = NFT_TRACETYPE_RULE;
-		info->nf_trace = pkt->skb->nf_trace;
+
+		if (info->trace)
+			info->nf_trace = info->pkt->skb->nf_trace;
 		break;
 	}
 
@@ -271,10 +270,10 @@ nft_do_chain(struct nft_pktinfo *pkt, void *priv)
 		switch (regs.verdict.code) {
 		case NFT_BREAK:
 			regs.verdict.code = NFT_CONTINUE;
-			nft_trace_copy_nftrace(&info);
+			nft_trace_copy_nftrace(pkt, &info);
 			continue;
 		case NFT_CONTINUE:
-			nft_trace_packet(&info, chain, rule,
+			nft_trace_packet(pkt, &info, chain, rule,
 					 NFT_TRACETYPE_RULE);
 			continue;
 		}
@@ -318,7 +317,7 @@ nft_do_chain(struct nft_pktinfo *pkt, void *priv)
 		goto next_rule;
 	}
 
-	nft_trace_packet(&info, basechain, NULL, NFT_TRACETYPE_POLICY);
+	nft_trace_packet(pkt, &info, basechain, NULL, NFT_TRACETYPE_POLICY);
 
 	if (static_branch_unlikely(&nft_counters_enabled))
 		nft_update_chain_stats(basechain, pkt);
-- 
2.35.1

[PATCH nf 2/2] selftests: netfilter: add test case for nf trace infrastructure

[Florian Westphal]

Enable/disable tracing infrastructure while packets are in-flight.
This triggers KASAN splat after
e34b9ed96ce3 ("netfilter: nf_tables: avoid skb access on nf_stolen").

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 .../selftests/netfilter/nft_trans_stress.sh   | 78 ++++++++++++++++++-
 1 file changed, 76 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/netfilter/nft_trans_stress.sh b/tools/testing/selftests/netfilter/nft_trans_stress.sh
index f1affd12c4b1..4a14bca99dee 100755
--- a/tools/testing/selftests/netfilter/nft_trans_stress.sh
+++ b/tools/testing/selftests/netfilter/nft_trans_stress.sh
@@ -9,8 +9,27 @@
 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
 
-testns=testns1
+testns=testns-$(mktemp -u "XXXXXXXX")
+
 tables="foo bar baz quux"
+global_ret=0
+eret=0
+lret=0
+
+check_result()
+{
+	local r=$1
+	local OK="PASS"
+
+	if [ $r -ne 0 ] ;then
+		OK="FAIL"
+		global_ret=$r
+	fi
+
+	echo "$OK: nft $2 test returned $r"
+
+	eret=0
+}
 
 nft --version > /dev/null 2>&1
 if [ $? -ne 0 ];then
@@ -59,20 +78,75 @@ done)
 
 sleep 1
 
+ip netns exec "$testns" nft -f "$tmp"
 for i in $(seq 1 10) ; do ip netns exec "$testns" nft -f "$tmp" & done
 
 for table in $tables;do
 	randsleep=$((RANDOM%10))
 	sleep $randsleep
-	ip netns exec "$testns" nft delete table inet $table 2>/dev/null
+	ip netns exec "$testns" nft delete table inet $table # 2>/dev/null
+	lret=$?
+	if [ $lret -ne 0 ]; then
+		eret=$lret
+	fi
 done
 
+check_result $eret "add/delete"
+
 randsleep=$((RANDOM%10))
 sleep $randsleep
 
+for i in $(seq 1 10) ; do
+	(echo "flush ruleset"; cat "$tmp") | ip netns exec "$testns" nft -f /dev/stdin
+
+	lret=$?
+	if [ $lret -ne 0 ]; then
+		eret=$lret
+	fi
+done
+
+check_result $eret "reload"
+
+for i in $(seq 1 10) ; do
+	(echo "flush ruleset"; cat "$tmp"
+	 echo "insert rule inet foo INPUT meta nftrace set 1"
+	 echo "insert rule inet foo OUTPUT meta nftrace set 1"
+	 ) | ip netns exec "$testns" nft -f /dev/stdin
+	lret=$?
+	if [ $lret -ne 0 ]; then
+		eret=$lret
+	fi
+
+	(echo "flush ruleset"; cat "$tmp"
+	 ) | ip netns exec "$testns" nft -f /dev/stdin
+
+	lret=$?
+	if [ $lret -ne 0 ]; then
+		eret=$lret
+	fi
+done
+
+check_result $eret "add/delete with nftrace enabled"
+
+echo "insert rule inet foo INPUT meta nftrace set 1" >> $tmp
+echo "insert rule inet foo OUTPUT meta nftrace set 1" >> $tmp
+
+for i in $(seq 1 10) ; do
+	(echo "flush ruleset"; cat "$tmp") | ip netns exec "$testns" nft -f /dev/stdin
+
+	lret=$?
+	if [ $lret -ne 0 ]; then
+		eret=1
+	fi
+done
+
+check_result $lret "add/delete with nftrace enabled"
+
 pkill -9 ping
 
 wait
 
 rm -f "$tmp"
 ip netns del "$testns"
+
+exit $global_ret
-- 
2.35.1