[PATCH 5.4 008/152] net: sched: correct flower port blocking

Greg Kroah-Hartman
2020-03-03T17:52:38Z

From: Jason Baron <jbaron@akamai.com>

[ Upstream commit 8a9093c79863b58cc2f9874d7ae788f0d622a596 ]

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/flow_dissector.h | 9 +++++++++
net/sched/cls_flower.c | 1 +
2 files changed, 10 insertions(+)

--- 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>

/**
@@ -338,4 +339,12 @@ 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
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -303,6 +303,7 @@ static int fl_classify(struct sk_buff *s
struct cls_fl_filter *f;

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_flow_dissect_meta(skb, &mask->dissector, &skb_key);