net-packet: fix null pointer exception in rollover mode

Rollover can be enabled as flag or mode. Allocate state in both cases.
This solves a NULL pointer exception in fanout_demux_rollover on
referencing po->rollover if using mode rollover.

Also make sure that in rollover mode each silo is tried (contrary
to rollover flag, where the main socket is excluded after an initial
try_self).

Tested:
  Passes tools/testing/net/psock_fanout.c, which tests both modes and
  flag. My previous tests were limited to bench_rollover, which only
  stresses the flag. The test now completes safely. it still gives an
  error for mode rollover, because it does not expect the new headroom
  (ROOM_NORMAL) requirement. I will send a separate patch to the test.

Fixes: 0648ab70afe6 ("packet: rollover prepare: per-socket state")

Signed-off-by: Willem de Bruijn <willemb@google.com>
----

I should have run this test and caught this before submission, of
course. Apologies for the oversight.
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index c30d147..fd51641 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1389,7 +1389,7 @@ static unsigned int fanout_demux_rollover(struct packet_fanout *f,
                                          unsigned int idx, bool try_self,
                                          unsigned int num)
 {
-       struct packet_sock *po, *po_next;
+       struct packet_sock *po, *po_next, *po_skip = NULL;
        unsigned int i, j, room = ROOM_NONE;
 
        po = pkt_sk(f->arr[idx]);
@@ -1399,12 +1399,13 @@ static unsigned int fanout_demux_rollover(struct packet_fanout *f,
                if (room == ROOM_NORMAL ||
                    (room == ROOM_LOW && !fanout_flow_is_huge(po, skb)))
                        return idx;
+               po_skip = po;
        }
 
        i = j = min_t(int, po->rollover->sock, num - 1);
        do {
                po_next = pkt_sk(f->arr[i]);
-               if (po_next != po && !po_next->pressure &&
+               if (po_next != po_skip && !po_next->pressure &&
                    packet_rcv_has_room(po_next, skb) == ROOM_NORMAL) {
                        if (i != j)
                                po->rollover->sock = i;
@@ -1549,7 +1550,8 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
        if (po->fanout)
                return -EALREADY;
 
-       if (type_flags & PACKET_FANOUT_FLAG_ROLLOVER) {
+       if (type == PACKET_FANOUT_ROLLOVER ||
+           (type_flags & PACKET_FANOUT_FLAG_ROLLOVER)) {
                po->rollover = kzalloc(sizeof(*po->rollover), GFP_KERNEL);
                if (!po->rollover)
                        return -ENOMEM;