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Message-ID: <ZLA0ILTAZsIzxR6c@debian.debian>
Date: Thu, 13 Jul 2023 10:28:00 -0700
From: Yan Zhai <yan@...udflare.com>
To: "open list:NETWORKING [TCP]" <netdev@...r.kernel.org>
Cc: kernel-team@...udflare.com, Eric Dumazet <edumazet@...gle.com>,
"David S. Miller" <davem@...emloft.net>,
David Ahern <dsahern@...nel.org>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
Xin Long <lucien.xin@...il.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
Andrew Melnychenko <andrew@...nix.com>,
Jason Wang <jasowang@...hat.com>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>,
open list <linux-kernel@...r.kernel.org>,
"open list:SCTP PROTOCOL" <linux-sctp@...r.kernel.org>
Subject: [PATCH v2 net] gso: fix dodgy bit handling for GSO_UDP_L4
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:
https://lore.kernel.org/all/CAJPywTKDdjtwkLVUW6LRA2FU912qcDmQOQGt2WaDo28KzYDg+A@mail.gmail.com/
This change restores the expected behavior of GSO_UDP_L4 packets.
Fixes: 1fd54773c267 ("udp: allow header check for dodgy GSO_UDP_L4 packets.")
Suggested-by: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Signed-off-by: Yan Zhai <yan@...udflare.com>
---
v2: dropped modifications to tcp/sctp on DODGY bit removal after
validating gso_segs. Also moved the UDP header check into
__udp_gso_segment (per Willem's suggestion).
---
net/ipv4/udp_offload.c | 16 +++++++++++-----
net/ipv6/udp_offload.c | 3 +--
2 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 75aa4de5b731..f402946da344 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -274,13 +274,20 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
__sum16 check;
__be16 newlen;
- if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)
- return __udp_gso_segment_list(gso_skb, features, is_ipv6);
-
mss = skb_shinfo(gso_skb)->gso_size;
if (gso_skb->len <= sizeof(*uh) + mss)
return ERR_PTR(-EINVAL);
+ if (skb_gso_ok(gso_skb, features | NETIF_F_GSO_ROBUST)) {
+ /* Packet is from an untrusted source, reset gso_segs. */
+ skb_shinfo(gso_skb)->gso_segs = DIV_ROUND_UP(gso_skb->len - sizeof(*uh),
+ mss);
+ return NULL;
+ }
+
+ if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)
+ return __udp_gso_segment_list(gso_skb, features, is_ipv6);
+
skb_pull(gso_skb, sizeof(*uh));
/* clear destructor to avoid skb_segment assigning it to tail */
@@ -388,8 +395,7 @@ 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))
+ if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
return __udp_gso_segment(skb, features, false);
mss = skb_shinfo(skb)->gso_size;
diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
index ad3b8726873e..09fa7a42cb93 100644
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -43,8 +43,7 @@ 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))
+ if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
return __udp_gso_segment(skb, features, true);
mss = skb_shinfo(skb)->gso_size;
--
2.30.2
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