Commit 8a9093c7 authored Feb 17, 2020 by Jason Baron Committed by David S. Miller Feb 17, 2020

net: sched: correct flower port blocking



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: 62230715 ("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>

parent a8154104

include/net/flow_dissector.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -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>

		struct sk_buff;
		@@ -348,4 +349,12 @@ 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

net/sched/cls_flower.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -305,6 +305,7 @@ static int fl_classify(struct sk_buff skb, const struct tcf_proto tp,
		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);

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