xfrm: Force a dst refcount before entering the xfrm type handlers

Crypto requests might return asynchronous. In this case we leave
the rcu protected region, so force a refcount on the skb's
destination entry before we enter the xfrm type input/output
handlers.

This fixes a crash when a route is deleted whilst sending IPsec
data that is transformed by an asynchronous algorithm.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 4 insertions, 0 deletions

diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
index 872065ca7f8c..341cd1189f8a 100644
--- a/net/xfrm/xfrm_input.c
+++ b/net/xfrm/xfrm_input.c
@@ -190,6 +190,8 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
                 XFRM_SKB_CB(skb)->seq.input.low = seq;
                 XFRM_SKB_CB(skb)->seq.input.hi = seq_hi;
 
+                skb_dst_force(skb);
+
                 nexthdr = x->type->input(x, skb);
 
                 if (nexthdr == -EINPROGRESS)
diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c
index 1aba03f449cc..8f3f0eedc5a4 100644
--- a/net/xfrm/xfrm_output.c
+++ b/net/xfrm/xfrm_output.c
@@ -78,6 +78,8 @@ static int xfrm_output_one(struct sk_buff *skb, int err)
 
                 spin_unlock_bh(&x->lock);
 
+                skb_dst_force(skb);
+
                 err = x->type->output(x, skb);
                 if (err == -EINPROGRESS)
                         goto out_exit;