[net] net: sched: correct flower port blocking
diff mbox series

Message ID 1581625699-24457-1-git-send-email-jbaron@akamai.com
State Changes Requested
Delegated to: David Miller
Headers show
Series
  • [net] net: sched: correct flower port blocking
Related show

Commit Message

Jason Baron Feb. 13, 2020, 8:28 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>
Signed-off-by: Jason Baron <jbaron@akamai.com>
---
 include/linux/skbuff.h | 8 ++++++++
 net/sched/cls_flower.c | 1 +
 2 files changed, 9 insertions(+)

Comments

Cong Wang Feb. 13, 2020, 10:50 p.m. UTC | #1
On Thu, Feb 13, 2020 at 12:31 PM Jason Baron <jbaron@akamai.com> wrote:
>
> 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>
> Signed-off-by: Jason Baron <jbaron@akamai.com>
> ---
>  include/linux/skbuff.h | 8 ++++++++
>  net/sched/cls_flower.c | 1 +
>  2 files changed, 9 insertions(+)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index ca8806b..f953bfa 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -1288,6 +1288,14 @@ bool __skb_flow_dissect(const struct net *net,
>                         void *data, __be16 proto, int nhoff, int hlen,
>                         unsigned int flags);
>
> +static inline void
> +skb_flow_dissect_init_key(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));
> +}

I think this function has nothing to do with skb, therefore it fits
better in include/net/flow_dissector.h? And remove skb prefix from
its name too.

Other than this:

Acked-by: Cong Wang <xiyou.wangcong@gmail.com>

Thanks.

Patch
diff mbox series

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ca8806b..f953bfa 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1288,6 +1288,14 @@  bool __skb_flow_dissect(const struct net *net,
 			void *data, __be16 proto, int nhoff, int hlen,
 			unsigned int flags);
 
+static inline void
+skb_flow_dissect_init_key(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));
+}
+
 static inline bool skb_flow_dissect(const struct sk_buff *skb,
 				    struct flow_dissector *flow_dissector,
 				    void *target_container, unsigned int flags)
diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index f9c0d1e..b0a534b 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) {
+		skb_flow_dissect_init_key(&skb_key.control, &skb_key.basic);
 		fl_clear_masked_range(&skb_key, mask);
 
 		skb_flow_dissect_meta(skb, &mask->dissector, &skb_key);