SKB_GSO_DODGY bit indicates a GSO packet comes from an untrusted source.
The canonical way is to recompute the gso_segs to avoid device driver
issues. Afterwards, the DODGY bit can be removed to avoid re-check at the
egress of later devices, e.g. packets can egress to a vlan device backed
by a real NIC.
Commit 1fd54773c267 ("udp: allow header check for dodgy GSO_UDP_L4
packets.") checks DODGY bit for UDP, but for packets that can be fed
directly to the device after gso_segs reset, it actually falls through
to fragmentation [1].
Commit 90017accff61 ("sctp: Add GSO support") and commit 3820c3f3e417
("[TCP]: Reset gso_segs if packet is dodgy") both didn't remove the DODGY
bit after recomputing gso_segs.
This change fixes the GSO_UDP_L4 handling case, and remove the DODGY bit
at other places.
Fixes: 90017accff61 ("sctp: Add GSO support")
Fixes: 3820c3f3e417 ("[TCP]: Reset gso_segs if packet is dodgy")
Fixes: 1fd54773c267 ("udp: allow header check for dodgy GSO_UDP_L4 packets.")
Signed-off-by: Yan Zhai <yan@xxxxxxxxxxxxxx>
---
[1]:
https://lore.kernel.org/all/CAJPywTKDdjtwkLVUW6LRA2FU912qcDmQOQGt2WaDo28KzYDg+A@xxxxxxxxxxxxxx/
---
net/ipv4/tcp_offload.c | 1 +
net/ipv4/udp_offload.c | 19 +++++++++++++++----
net/ipv6/udp_offload.c | 19 +++++++++++++++----
net/sctp/offload.c | 2 ++
4 files changed, 33 insertions(+), 8 deletions(-)
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 8311c38267b5..f9b93708c22e 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -87,6 +87,7 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
/* Packet is from an untrusted source, reset gso_segs. */
skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
+ skb_shinfo(skb)->gso_type &= ~SKB_GSO_DODGY;
segs = NULL;
goto out;
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 75aa4de5b731..bd29cf19bb6b 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -388,11 +388,22 @@ static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
if (!pskb_may_pull(skb, sizeof(struct udphdr)))
goto out;
- if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4 &&
- !skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST))
- return __udp_gso_segment(skb, features, false);
-
mss = skb_shinfo(skb)->gso_size;
+
+ if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4) {
+ if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
+ /* Packet is from an untrusted source, reset actual gso_segs */
+ skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len - sizeof(*uh),
+ mss);
+ skb_shinfo(skb)->gso_type &= ~SKB_GSO_DODGY;
+
+ segs = NULL;
+ goto out;
+ } else {
+ return __udp_gso_segment(skb, features, false);
+ }
+ }
+
if (unlikely(skb->len <= mss))
goto out;
diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
index ad3b8726873e..6857d9f7bd06 100644
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -43,11 +43,22 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
if (!pskb_may_pull(skb, sizeof(struct udphdr)))
goto out;
- if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4 &&
- !skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST))
- return __udp_gso_segment(skb, features, true);
-
mss = skb_shinfo(skb)->gso_size;
+
+ if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4) {
+ if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
+ /* Packet is from an untrusted source, reset actual gso_segs */
+ skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len - sizeof(*uh),
+ mss);
+ skb_shinfo(skb)->gso_type &= ~SKB_GSO_DODGY;
+
+ segs = NULL;
+ goto out;
+ } else {
+ return __udp_gso_segment(skb, features, true);
+ }
+ }
+
if (unlikely(skb->len <= mss))
goto out;
diff --git a/net/sctp/offload.c b/net/sctp/offload.c
index 502095173d88..3d2b44db0d42 100644
--- a/net/sctp/offload.c
+++ b/net/sctp/offload.c
@@ -65,6 +65,8 @@ static struct sk_buff *sctp_gso_segment(struct sk_buff *skb,
skb_walk_frags(skb, frag_iter)
pinfo->gso_segs++;
+ pinfo->gso_type &= ~SKB_GSO_DODGY;
+
segs = NULL;
goto out;
}
--
2.30.2
