[PATCH v1] gro: bug fix in identifying 0 length tcp packets

[PATCH v1] gro: bug fix in identifying 0 length tcp packets

[Kumara Parameshwaran]

As the minimum Ethernet frame size is 64 bytes, a 0 length
tcp payload without tcp options would be 54 bytes and hence
there would be padding. So it would be incorrect to use the
packet length to determine the tcp data length.

Fixes: 1e4cf4d6d4fb ("gro: cleanup")
Cc: stable@dpdk.org

Signed-off-by: Kumara Parameshwaran <kparameshwar@vmware.com>
---
v1:
	Do not use packet length to determine the tcp data length as 
	the packet length could have padded bytes. This would lead 
	to addition of 0 length tcp packets into the GRO layer when 
	there ethernet fram is padded.
 lib/gro/gro_tcp4.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/lib/gro/gro_tcp4.c b/lib/gro/gro_tcp4.c
index 7498c66..45e3f48 100644
--- a/lib/gro/gro_tcp4.c
+++ b/lib/gro/gro_tcp4.c
@@ -198,7 +198,7 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
 	struct rte_tcp_hdr *tcp_hdr;
 	uint32_t sent_seq;
 	int32_t tcp_dl;
-	uint16_t ip_id, hdr_len, frag_off;
+	uint16_t ip_id, frag_off;
 	uint8_t is_atomic;
 
 	struct tcp4_flow_key key;
@@ -217,7 +217,6 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
 	eth_hdr = rte_pktmbuf_mtod(pkt, struct rte_ether_hdr *);
 	ipv4_hdr = (struct rte_ipv4_hdr *)((char *)eth_hdr + pkt->l2_len);
 	tcp_hdr = (struct rte_tcp_hdr *)((char *)ipv4_hdr + pkt->l3_len);
-	hdr_len = pkt->l2_len + pkt->l3_len + pkt->l4_len;
 
 	/*
 	 * Don't process the packet which has FIN, SYN, RST, PSH, URG, ECE
@@ -229,7 +228,7 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
 	 * Don't process the packet whose payload length is less than or
 	 * equal to 0.
 	 */
-	tcp_dl = pkt->pkt_len - hdr_len;
+	tcp_dl = rte_be_to_cpu_16(ipv4_hdr->total_length) - (pkt->l3_len + pkt->l4_len);
 	if (tcp_dl <= 0)
 		return -1;
 
-- 
2.7.4

RE: [PATCH v1] gro: bug fix in identifying 0 length tcp packets

[Morten Brørup]

> From: Kumara Parameshwaran [mailto:kumaraparamesh92@gmail.com]
> Sent: Sunday, 3 April 2022 13.51
> 
> As the minimum Ethernet frame size is 64 bytes, a 0 length
> tcp payload without tcp options would be 54 bytes and hence
> there would be padding. So it would be incorrect to use the
> packet length to determine the tcp data length.
> 
> Fixes: 1e4cf4d6d4fb ("gro: cleanup")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Kumara Parameshwaran <kparameshwar@vmware.com>
> ---
> v1:
> 	Do not use packet length to determine the tcp data length as
> 	the packet length could have padded bytes. This would lead
> 	to addition of 0 length tcp packets into the GRO layer when
> 	there ethernet fram is padded.
>  lib/gro/gro_tcp4.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/gro/gro_tcp4.c b/lib/gro/gro_tcp4.c
> index 7498c66..45e3f48 100644
> --- a/lib/gro/gro_tcp4.c
> +++ b/lib/gro/gro_tcp4.c
> @@ -198,7 +198,7 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
>  	struct rte_tcp_hdr *tcp_hdr;
>  	uint32_t sent_seq;
>  	int32_t tcp_dl;
> -	uint16_t ip_id, hdr_len, frag_off;
> +	uint16_t ip_id, frag_off;
>  	uint8_t is_atomic;
> 
>  	struct tcp4_flow_key key;
> @@ -217,7 +217,6 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
>  	eth_hdr = rte_pktmbuf_mtod(pkt, struct rte_ether_hdr *);
>  	ipv4_hdr = (struct rte_ipv4_hdr *)((char *)eth_hdr + pkt-
> >l2_len);
>  	tcp_hdr = (struct rte_tcp_hdr *)((char *)ipv4_hdr + pkt->l3_len);
> -	hdr_len = pkt->l2_len + pkt->l3_len + pkt->l4_len;
> 
>  	/*
>  	 * Don't process the packet which has FIN, SYN, RST, PSH, URG,
> ECE
> @@ -229,7 +228,7 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
>  	 * Don't process the packet whose payload length is less than or
>  	 * equal to 0.
>  	 */
> -	tcp_dl = pkt->pkt_len - hdr_len;
> +	tcp_dl = rte_be_to_cpu_16(ipv4_hdr->total_length) - (pkt->l3_len
> + pkt->l4_len);
>  	if (tcp_dl <= 0)
>  		return -1;
> 
> --
> 2.7.4
> 

Please confirm that this does not introduce a buffer overrun regarding malformed packets, e.g. a small packet with ipv4_hdr->total_length set to 65000.

I haven't looked at the patch in context, so my concern may be irrelevant.

-Morten

[PATCH v2] gro: bug fix in identifying 0 length tcp packets

[Kumara Parameshwaran]

From: Kumara Parameshwaran <kumaraparamesh92@gmail.com>

As the minimum Ethernet frame size is 64 bytes, a 0 length
tcp payload without tcp options would be 54 bytes and hence
there would be padding. So it would be incorrect to use the
packet length to determine the tcp data length.

Fixes: 1e4cf4d6d4fb ("gro: cleanup")
Cc: stable@dpdk.org

Signed-off-by: Kumara Parameshwaran <kparameshwar@vmware.com>
---
v1:
	Do not use packet length to determine the tcp data length as 
	the packet length could have padded bytes. This would lead 
	to addition of 0 length tcp packets into the GRO layer when 
	there ethernet fram is padded.
v2:
	Since using ip packet length to determine the tcp data length, 
	validate the ip packet length

 lib/gro/gro_tcp4.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/gro/gro_tcp4.c b/lib/gro/gro_tcp4.c
index 7498c66..30f5922 100644
--- a/lib/gro/gro_tcp4.c
+++ b/lib/gro/gro_tcp4.c
@@ -198,7 +198,8 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
 	struct rte_tcp_hdr *tcp_hdr;
 	uint32_t sent_seq;
 	int32_t tcp_dl;
-	uint16_t ip_id, hdr_len, frag_off;
+	uint16_t ip_id, frag_off;
+	uint16_t ip_len;
 	uint8_t is_atomic;
 
 	struct tcp4_flow_key key;
@@ -217,7 +218,6 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
 	eth_hdr = rte_pktmbuf_mtod(pkt, struct rte_ether_hdr *);
 	ipv4_hdr = (struct rte_ipv4_hdr *)((char *)eth_hdr + pkt->l2_len);
 	tcp_hdr = (struct rte_tcp_hdr *)((char *)ipv4_hdr + pkt->l3_len);
-	hdr_len = pkt->l2_len + pkt->l3_len + pkt->l4_len;
 
 	/*
 	 * Don't process the packet which has FIN, SYN, RST, PSH, URG, ECE
@@ -229,8 +229,9 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
 	 * Don't process the packet whose payload length is less than or
 	 * equal to 0.
 	 */
-	tcp_dl = pkt->pkt_len - hdr_len;
-	if (tcp_dl <= 0)
+	ip_len = rte_be_to_cpu_16(ipv4_hdr->total_length);
+	tcp_dl = ip_len - (pkt->l3_len + pkt->l4_len);
+	if (tcp_dl <= 0 || ip_len > pkt->pkt_len)
 		return -1;
 
 	/*
-- 
2.7.4