[PATCH nf] netfilter: flowtable: set NF_FLOW_TEARDOWN flag on entry expiration

[PATCH nf] netfilter: flowtable: set NF_FLOW_TEARDOWN flag on entry expiration

[Pablo Neira Ayuso]

If the flow timer expires, the gc sets on the NF_FLOW_TEARDOWN flag.
Otherwise, the flowtable software path might race to refresh the
timeout, leaving the state machine in inconsistent state.

Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
Reported-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_flow_table_core.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
index 4344e572b7f9..42da6e337276 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -284,7 +284,7 @@ static void flow_offload_del(struct nf_flowtable *flow_table,
 
 	if (nf_flow_has_expired(flow))
 		flow_offload_fixup_ct(flow->ct);
-	else if (test_bit(NF_FLOW_TEARDOWN, &flow->flags))
+	else
 		flow_offload_fixup_ct_timeout(flow->ct);
 
 	flow_offload_free(flow);
@@ -361,8 +361,10 @@ static void nf_flow_offload_gc_step(struct flow_offload *flow, void *data)
 {
 	struct nf_flowtable *flow_table = data;
 
-	if (nf_flow_has_expired(flow) || nf_ct_is_dying(flow->ct) ||
-	    test_bit(NF_FLOW_TEARDOWN, &flow->flags)) {
+	if (nf_flow_has_expired(flow) || nf_ct_is_dying(flow->ct))
+		set_bit(NF_FLOW_TEARDOWN, &flow->flags);
+
+	if (test_bit(NF_FLOW_TEARDOWN, &flow->flags)) {
 		if (test_bit(NF_FLOW_HW, &flow->flags)) {
 			if (!test_bit(NF_FLOW_HW_DYING, &flow->flags))
 				nf_flow_offload_del(flow_table, flow);
-- 
2.20.1

Re: [PATCH nf] netfilter: flowtable: set NF_FLOW_TEARDOWN flag on entry expiration

[Roi Dayan]

On 2020-05-11 1:17 PM, Pablo Neira Ayuso wrote:
> If the flow timer expires, the gc sets on the NF_FLOW_TEARDOWN flag.
> Otherwise, the flowtable software path might race to refresh the
> timeout, leaving the state machine in inconsistent state.
> 
> Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
> Reported-by: Paul Blakey <paulb@mellanox.com>
> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
> ---
>  net/netfilter/nf_flow_table_core.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
> index 4344e572b7f9..42da6e337276 100644
> --- a/net/netfilter/nf_flow_table_core.c
> +++ b/net/netfilter/nf_flow_table_core.c
> @@ -284,7 +284,7 @@ static void flow_offload_del(struct nf_flowtable *flow_table,
>  
>  	if (nf_flow_has_expired(flow))
>  		flow_offload_fixup_ct(flow->ct);
> -	else if (test_bit(NF_FLOW_TEARDOWN, &flow->flags))
> +	else
>  		flow_offload_fixup_ct_timeout(flow->ct);
>  
>  	flow_offload_free(flow);
> @@ -361,8 +361,10 @@ static void nf_flow_offload_gc_step(struct flow_offload *flow, void *data)
>  {
>  	struct nf_flowtable *flow_table = data;
>  
> -	if (nf_flow_has_expired(flow) || nf_ct_is_dying(flow->ct) ||
> -	    test_bit(NF_FLOW_TEARDOWN, &flow->flags)) {
> +	if (nf_flow_has_expired(flow) || nf_ct_is_dying(flow->ct))
> +		set_bit(NF_FLOW_TEARDOWN, &flow->flags);
> +
> +	if (test_bit(NF_FLOW_TEARDOWN, &flow->flags)) {
>  		if (test_bit(NF_FLOW_HW, &flow->flags)) {
>  			if (!test_bit(NF_FLOW_HW_DYING, &flow->flags))
>  				nf_flow_offload_del(flow_table, flow);
> 

thanks

Reviewed-by: Roi Dayan <roid@mellanox.com>