[PATCH ipsec v6] xfrm: replay: Fix ESN wrap around for GSO

[Christian Langrock <christian.langrock@secunet.com>]

When using GSO it can happen that the wrong seq_hi is used for the last
packets before the wrap around. This can lead to double usage of a
sequence number. To avoid this, we should serialize this last GSO
packet.

Fixes: d7dbefc45cf5 ("xfrm: Add xfrm_replay_overflow functions for offloading")
Co-developed-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Christian Langrock <christian.langrock@secunet.com>
---
Changes in v6:
 - move overflow check to offloading path to avoid locking issues

Changes in v5:
 - Fix build

Changes in v4:
 - move changelog within comment
 - add reviewer

Changes in v3:
- fix build
- remove wrapper function

Changes in v2:
- switch to bool as return value
- remove switch case in wrapper function
---
 net/ipv4/esp4_offload.c |  3 +++
 net/ipv6/esp6_offload.c |  3 +++
 net/xfrm/xfrm_device.c  | 15 ++++++++++++++-
 net/xfrm/xfrm_replay.c  |  2 +-
 4 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/esp4_offload.c b/net/ipv4/esp4_offload.c
index 170152772d33..3969fa805679 100644
--- a/net/ipv4/esp4_offload.c
+++ b/net/ipv4/esp4_offload.c
@@ -314,6 +314,9 @@ static int esp_xmit(struct xfrm_state *x, struct sk_buff *skb,  netdev_features_
                        xo->seq.low += skb_shinfo(skb)->gso_segs;
        }
 
+       if (xo->seq.low < seq)
+               xo->seq.hi++;
+
        esp.seqno = cpu_to_be64(seq + ((u64)xo->seq.hi << 32));
 
        ip_hdr(skb)->tot_len = htons(skb->len);
diff --git a/net/ipv6/esp6_offload.c b/net/ipv6/esp6_offload.c
index 79d43548279c..242f4295940e 100644
--- a/net/ipv6/esp6_offload.c
+++ b/net/ipv6/esp6_offload.c
@@ -346,6 +346,9 @@ static int esp6_xmit(struct xfrm_state *x, struct sk_buff *skb,  netdev_features
                        xo->seq.low += skb_shinfo(skb)->gso_segs;
        }
 
+       if (xo->seq.low < seq)
+               xo->seq.hi++;
+
        esp.seqno = cpu_to_be64(xo->seq.low + ((u64)xo->seq.hi << 32));
 
        len = skb->len - sizeof(struct ipv6hdr);
diff --git a/net/xfrm/xfrm_device.c b/net/xfrm/xfrm_device.c
index 5f5aafd418af..21269e8f2db4 100644
--- a/net/xfrm/xfrm_device.c
+++ b/net/xfrm/xfrm_device.c
@@ -97,6 +97,18 @@ static void xfrm_outer_mode_prep(struct xfrm_state *x, struct sk_buff *skb)
        }
 }
 
+static inline bool xmit_xfrm_check_overflow(struct sk_buff *skb)
+{
+       struct xfrm_offload *xo = xfrm_offload(skb);
+       __u32 seq = xo->seq.low;
+
+       seq += skb_shinfo(skb)->gso_segs;
+       if (unlikely(seq < xo->seq.low))
+               return true;
+
+       return false;
+}
+
 struct sk_buff *validate_xmit_xfrm(struct sk_buff *skb, netdev_features_t features, bool *again)
 {
        int err;
@@ -134,7 +146,8 @@ struct sk_buff *validate_xmit_xfrm(struct sk_buff *skb, netdev_features_t featur
                return skb;
        }
 
-       if (skb_is_gso(skb) && unlikely(x->xso.dev != dev)) {
+       if (skb_is_gso(skb) && (unlikely(x->xso.dev != dev) ||
+                               unlikely(xmit_xfrm_check_overflow(skb)))) {
                struct sk_buff *segs;
 
                /* Packet got rerouted, fixup features and segment it. */
diff --git a/net/xfrm/xfrm_replay.c b/net/xfrm/xfrm_replay.c
index 9f4d42eb090f..ce56d659c55a 100644
--- a/net/xfrm/xfrm_replay.c
+++ b/net/xfrm/xfrm_replay.c
@@ -714,7 +714,7 @@ static int xfrm_replay_overflow_offload_esn(struct xfrm_state *x, struct sk_buff
                        oseq += skb_shinfo(skb)->gso_segs;
                }
 
-               if (unlikely(oseq < replay_esn->oseq)) {
+               if (unlikely(xo->seq.low < replay_esn->oseq)) {
                        XFRM_SKB_CB(skb)->seq.output.hi = ++oseq_hi;
                        xo->seq.hi = oseq_hi;
                        replay_esn->oseq_hi = oseq_hi;

base-commit: 0326074ff4652329f2a1a9c8685104576bd8d131
-- 
2.37.1.223.g6a475b71f8