xfrm: Reset secpath in xfrm failure

In esp4_gro_receive() and esp6_gro_receive(), secpath can be allocated
without adding xfrm state to xvec. Then, sp->xvec[sp->len - 1] would
fail and result in dereferencing invalid pointer in esp4_gso_segment()
and esp6_gso_segment(). Reset secpath if xfrm function returns error.

Fixes: 7785bba ("esp: Add a software GRO codepath")
Reported-by: syzbot+b69368fd933c6c592f4c@syzkaller.appspotmail.com
Signed-off-by: Myungho Jung <mhjungk@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/ipv4/esp4_offload.c

@@ -52,21 +52,21 @@ static struct sk_buff *esp4_gro_receive(struct list_head *head,
 			goto out;
 
 		if (sp->len == XFRM_MAX_DEPTH)
-			goto out;
+			goto out_reset;
 
 		x = xfrm_state_lookup(dev_net(skb->dev), skb->mark,
 				      (xfrm_address_t *)&ip_hdr(skb)->daddr,
 				      spi, IPPROTO_ESP, AF_INET);
 		if (!x)
-			goto out;
+			goto out_reset;
 
 		sp->xvec[sp->len++] = x;
 		sp->olen++;
 
 		xo = xfrm_offload(skb);
 		if (!xo) {
 			xfrm_state_put(x);
-			goto out;
+			goto out_reset;
 		}
 	}
 
@@ -82,6 +82,8 @@ static struct sk_buff *esp4_gro_receive(struct list_head *head,
 	xfrm_input(skb, IPPROTO_ESP, spi, -2);
 
 	return ERR_PTR(-EINPROGRESS);
+out_reset:
+	secpath_reset(skb);
 out:
 	skb_push(skb, offset);
 	NAPI_GRO_CB(skb)->same_flow = 0;

net/ipv6/esp6_offload.c

@@ -74,21 +74,21 @@ static struct sk_buff *esp6_gro_receive(struct list_head *head,
 			goto out;
 
 		if (sp->len == XFRM_MAX_DEPTH)
-			goto out;
+			goto out_reset;
 
 		x = xfrm_state_lookup(dev_net(skb->dev), skb->mark,
 				      (xfrm_address_t *)&ipv6_hdr(skb)->daddr,
 				      spi, IPPROTO_ESP, AF_INET6);
 		if (!x)
-			goto out;
+			goto out_reset;
 
 		sp->xvec[sp->len++] = x;
 		sp->olen++;
 
 		xo = xfrm_offload(skb);
 		if (!xo) {
 			xfrm_state_put(x);
-			goto out;
+			goto out_reset;
 		}
 	}
 
@@ -109,6 +109,8 @@ static struct sk_buff *esp6_gro_receive(struct list_head *head,
 	xfrm_input(skb, IPPROTO_ESP, spi, -2);
 
 	return ERR_PTR(-EINPROGRESS);
+out_reset:
+	secpath_reset(skb);
 out:
 	skb_push(skb, offset);
 	NAPI_GRO_CB(skb)->same_flow = 0;