release/5.2.40/net-sched-correct-flower-port-blocking.patch

From 06d5273edf9cee3cd325e2ef551cd6098eacb2ab Mon Sep 17 00:00:00 2001
From: Jason Baron <jbaron@akamai.com>
Date: Mon, 17 Feb 2020 15:38:09 -0500
Subject: [PATCH] net: sched: correct flower port blocking

commit 8a9093c79863b58cc2f9874d7ae788f0d622a596 upstream.

tc flower rules that are based on src or dst port blocking are sometimes
ineffective due to uninitialized stack data. __skb_flow_dissect() extracts
ports from the skb for tc flower to match against. However, the port
dissection is not done when when the FLOW_DIS_IS_FRAGMENT bit is set in
key_control->flags. All callers of __skb_flow_dissect(), zero-out the
key_control field except for fl_classify() as used by the flower
classifier. Thus, the FLOW_DIS_IS_FRAGMENT may be set on entry to
__skb_flow_dissect(), since key_control is allocated on the stack
and may not be initialized.

Since key_basic and key_control are present for all flow keys, let's
make sure they are initialized.

Fixes: 62230715fd24 ("flow_dissector: do not dissect l4 ports for fragments")
Co-developed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jason Baron <jbaron@akamai.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index 441577a78636..457ac35050cf 100644
--- a/include/net/flow_dissector.h
+++ b/include/net/flow_dissector.h
@@ -5,6 +5,7 @@
 #include <linux/types.h>
 #include <linux/in6.h>
 #include <linux/siphash.h>
+#include <linux/string.h>
 #include <uapi/linux/if_ether.h>
 
 /**
@@ -314,4 +315,12 @@ struct bpf_flow_dissector {
 	void			*data_end;
 };
 
+static inline void
+flow_dissector_init_keys(struct flow_dissector_key_control *key_control,
+			 struct flow_dissector_key_basic *key_basic)
+{
+	memset(key_control, 0, sizeof(*key_control));
+	memset(key_basic, 0, sizeof(*key_basic));
+}
+
 #endif
diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index a9ef122916fd..295401c6f73e 100644
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -282,6 +282,7 @@ static int fl_classify(struct sk_buff *skb, const struct tcf_proto *tp,
 	struct fl_flow_key skb_mkey;
 
 	list_for_each_entry_rcu(mask, &head->masks, list) {
+		flow_dissector_init_keys(&skb_key.control, &skb_key.basic);
 		fl_clear_masked_range(&skb_key, mask);
 
 		skb_key.indev_ifindex = skb->skb_iif;
-- 
2.7.4