[PATCH net-next 2/3] rxrpc: Fix a null ptr deref in rxrpc_fill_out_ack()

[David Howells]

rxrpc_fill_out_ack() needs to be passed the connection pointer from its
caller rather than using call->conn as the call may be disconnected in
parallel with it, clearing call->conn, leading to:

        BUG: unable to handle kernel NULL pointer dereference at 
0000000000000010
        IP: rxrpc_send_ack_packet+0x231/0x6a4

Signed-off-by: David Howells <dhowe...@redhat.com>
---

 net/rxrpc/output.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index 71e6f713fbe7..8ee8b2d4a3eb 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -35,7 +35,8 @@ struct rxrpc_abort_buffer {
 /*
  * Fill out an ACK packet.
  */
-static size_t rxrpc_fill_out_ack(struct rxrpc_call *call,
+static size_t rxrpc_fill_out_ack(struct rxrpc_connection *conn,
+                                struct rxrpc_call *call,
                                 struct rxrpc_ack_buffer *pkt,
                                 rxrpc_seq_t *_hard_ack,
                                 rxrpc_seq_t *_top,
@@ -77,8 +78,8 @@ static size_t rxrpc_fill_out_ack(struct rxrpc_call *call,
                } while (before_eq(seq, top));
        }
 
-       mtu = call->conn->params.peer->if_mtu;
-       mtu -= call->conn->params.peer->hdrsize;
+       mtu = conn->params.peer->if_mtu;
+       mtu -= conn->params.peer->hdrsize;
        jmax = (call->nr_jumbo_bad > 3) ? 1 : rxrpc_rx_jumbo_max;
        pkt->ackinfo.rxMTU      = htonl(rxrpc_rx_mtu);
        pkt->ackinfo.maxMTU     = htonl(mtu);
@@ -148,7 +149,7 @@ int rxrpc_send_ack_packet(struct rxrpc_call *call, bool 
ping)
                }
                call->ackr_reason = 0;
        }
-       n = rxrpc_fill_out_ack(call, pkt, &hard_ack, &top, reason);
+       n = rxrpc_fill_out_ack(conn, call, pkt, &hard_ack, &top, reason);
 
        spin_unlock_bh(&call->lock);