Merge tag 'ipsec-2024-05-02' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec

Steffen Klassert says:

====================
pull request (net): ipsec 2024-05-02

1) Fix an error pointer dereference in xfrm_in_fwd_icmp.
   From Antony Antony.

2) Preserve vlan tags for ESP transport mode software GRO.
   From Paul Davey.

3) Fix a spelling mistake in an uapi xfrm.h comment.
   From Anotny Antony.

* tag 'ipsec-2024-05-02' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec:
  xfrm: Correct spelling mistake in xfrm.h comment
  xfrm: Preserve vlan tags for transport mode software GRO
  xfrm: fix possible derferencing in error path
====================

Link: https://lore.kernel.org/r/20240502084838.2269355-1-steffen.klassert@secunet.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

include/linux/skbuff.h

@@ -3031,6 +3031,21 @@ static inline void skb_mac_header_rebuild(struct sk_buff *skb)
 	}
 }
 
+/* Move the full mac header up to current network_header.
+ * Leaves skb->data pointing at offset skb->mac_len into the mac_header.
+ * Must be provided the complete mac header length.
+ */
+static inline void skb_mac_header_rebuild_full(struct sk_buff *skb, u32 full_mac_len)
+{
+	if (skb_mac_header_was_set(skb)) {
+		const unsigned char *old_mac = skb_mac_header(skb);
+
+		skb_set_mac_header(skb, -full_mac_len);
+		memmove(skb_mac_header(skb), old_mac, full_mac_len);
+		__skb_push(skb, full_mac_len - skb->mac_len);
+	}
+}
+
 static inline int skb_checksum_start_offset(const struct sk_buff *skb)
 {
 	return skb->csum_start - skb_headroom(skb);

include/net/xfrm.h

@@ -1049,6 +1049,9 @@ struct xfrm_offload {
 #define CRYPTO_INVALID_PACKET_SYNTAX		64
 #define CRYPTO_INVALID_PROTOCOL			128
 
+	/* Used to keep whole l2 header for transport mode GRO */
+	__u32			orig_mac_len;
+
 	__u8			proto;
 	__u8			inner_ipproto;
 };

include/uapi/linux/xfrm.h

@@ -228,7 +228,7 @@ enum {
 #define XFRM_NR_MSGTYPES (XFRM_MSG_MAX + 1 - XFRM_MSG_BASE)
 
 /*
- * Generic LSM security context for comunicating to user space
+ * Generic LSM security context for communicating to user space
  * NOTE: Same format as sadb_x_sec_ctx
  */
 struct xfrm_user_sec_ctx {

net/ipv4/xfrm4_input.c

@@ -63,7 +63,11 @@ int xfrm4_transport_finish(struct sk_buff *skb, int async)
 	ip_send_check(iph);
 
 	if (xo && (xo->flags & XFRM_GRO)) {
-		skb_mac_header_rebuild(skb);
+		/* The full l2 header needs to be preserved so that re-injecting the packet at l2
+		 * works correctly in the presence of vlan tags.
+		 */
+		skb_mac_header_rebuild_full(skb, xo->orig_mac_len);
+		skb_reset_network_header(skb);
 		skb_reset_transport_header(skb);
 		return 0;
 	}

net/ipv6/xfrm6_input.c

@@ -58,7 +58,11 @@ int xfrm6_transport_finish(struct sk_buff *skb, int async)
 	skb_postpush_rcsum(skb, skb_network_header(skb), nhlen);
 
 	if (xo && (xo->flags & XFRM_GRO)) {
-		skb_mac_header_rebuild(skb);
+		/* The full l2 header needs to be preserved so that re-injecting the packet at l2
+		 * works correctly in the presence of vlan tags.
+		 */
+		skb_mac_header_rebuild_full(skb, xo->orig_mac_len);
+		skb_reset_network_header(skb);
 		skb_reset_transport_header(skb);
 		return 0;
 	}

net/xfrm/xfrm_input.c

@@ -389,11 +389,15 @@ static int xfrm_prepare_input(struct xfrm_state *x, struct sk_buff *skb)
  */
 static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
 {
+	struct xfrm_offload *xo = xfrm_offload(skb);
 	int ihl = skb->data - skb_transport_header(skb);
 
 	if (skb->transport_header != skb->network_header) {
 		memmove(skb_transport_header(skb),
 			skb_network_header(skb), ihl);
+		if (xo)
+			xo->orig_mac_len =
+				skb_mac_header_was_set(skb) ? skb_mac_header_len(skb) : 0;
 		skb->network_header = skb->transport_header;
 	}
 	ip_hdr(skb)->tot_len = htons(skb->len + ihl);
@@ -404,11 +408,15 @@ static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
 static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
 {
 #if IS_ENABLED(CONFIG_IPV6)
+	struct xfrm_offload *xo = xfrm_offload(skb);
 	int ihl = skb->data - skb_transport_header(skb);
 
 	if (skb->transport_header != skb->network_header) {
 		memmove(skb_transport_header(skb),
 			skb_network_header(skb), ihl);
+		if (xo)
+			xo->orig_mac_len =
+				skb_mac_header_was_set(skb) ? skb_mac_header_len(skb) : 0;
 		skb->network_header = skb->transport_header;
 	}
 	ipv6_hdr(skb)->payload_len = htons(skb->len + ihl -

net/xfrm/xfrm_policy.c

@@ -3593,6 +3593,8 @@ xfrm_policy *xfrm_in_fwd_icmp(struct sk_buff *skb,
 			return pol;
 
 		pol = xfrm_policy_lookup(net, &fl1, family, XFRM_POLICY_FWD, if_id);
+		if (IS_ERR(pol))
+			pol = NULL;
 	}
 
 	return pol;