[v2,net] net: sched: correct flower port blocking
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Message ID 1581697224-20041-1-git-send-email-jbaron@akamai.com
State Accepted
Delegated to: David Miller
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Series
  • [v2,net] net: sched: correct flower port blocking
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Commit Message

Jason Baron Feb. 14, 2020, 4:20 p.m. UTC
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>
---
v2:

-move rename to flow_dissector_init_keys() amd move to
 flow_dissector.h (Cong Wang)

 include/net/flow_dissector.h | 8 ++++++++
 net/sched/cls_flower.c       | 1 +
 2 files changed, 9 insertions(+)

Comments

David Miller Feb. 17, 2020, 3:08 a.m. UTC | #1
From: Jason Baron <jbaron@akamai.com>
Date: Fri, 14 Feb 2020 11:20:24 -0500

> 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>

Applied and queued up for -stable.
David Miller Feb. 17, 2020, 3:18 a.m. UTC | #2
From: David Miller <davem@davemloft.net>
Date: Sun, 16 Feb 2020 19:08:12 -0800 (PST)

> From: Jason Baron <jbaron@akamai.com>
> Date: Fri, 14 Feb 2020 11:20:24 -0500
> 
>> 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>
> 
> Applied and queued up for -stable.

Actually this doesn't even compile:

In file included from drivers/net/ethernet/mellanox/mlx5/core/en_tc.c:33:
./include/net/flow_dissector.h: In function ‘flow_dissector_init_keys’:
./include/net/flow_dissector.h:355:2: error: implicit declaration of function ‘memset’ [-Werror=implicit-function-declaration]
  memset(key_control, 0, sizeof(*key_control));
  ^~~~~~
./include/net/flow_dissector.h:355:2: warning: incompatible implicit declaration of built-in function ‘memset’
./include/net/flow_dissector.h:355:2: note: include ‘<string.h>’ or provide a declaration of ‘memset’
./include/net/flow_dissector.h:9:1:
+#include <string.h>
 
./include/net/flow_dissector.h:355:2:
  memset(key_control, 0, sizeof(*key_control));
  ^~~~~~

Patch
diff mbox series

diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index d93017a..4bd4931 100644
--- a/include/net/flow_dissector.h
+++ b/include/net/flow_dissector.h
@@ -349,4 +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
diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index f9c0d1e..b783254 100644
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -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);