net: introduce qemu_receive_packet()

Some NIC supports loopback mode and this is done by calling
nc->info->receive() directly which in fact suppresses the effort of
reentrancy check that is done in qemu_net_queue_send().

Unfortunately we can't use qemu_net_queue_send() here since for
loopback there's no sender as peer, so this patch introduce a
qemu_receive_packet() which is used for implementing loopback mode
for a NIC with this check.

NIC that supports loopback mode will be converted to this helper.

This is intended to address CVE-2021-3416.

Cc: Prasad J Pandit <ppandit@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Jason Wang <jasowang@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/net/net.h b/include/net/net.h
index 919facaad2..4f56cae0fa 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -144,12 +144,17 @@ void *qemu_get_nic_opaque(NetClientState *nc);
 void qemu_del_net_client(NetClientState *nc);
 typedef void (*qemu_nic_foreach)(NICState *nic, void *opaque);
 void qemu_foreach_nic(qemu_nic_foreach func, void *opaque);
+int qemu_can_receive_packet(NetClientState *nc);
 int qemu_can_send_packet(NetClientState *nc);
 ssize_t qemu_sendv_packet(NetClientState *nc, const struct iovec *iov,
                           int iovcnt);
 ssize_t qemu_sendv_packet_async(NetClientState *nc, const struct iovec *iov,
                                 int iovcnt, NetPacketSent *sent_cb);
 ssize_t qemu_send_packet(NetClientState *nc, const uint8_t *buf, int size);
+ssize_t qemu_receive_packet(NetClientState *nc, const uint8_t *buf, int size);
+ssize_t qemu_receive_packet_iov(NetClientState *nc,
+                                const struct iovec *iov,
+                                int iovcnt);
 ssize_t qemu_send_packet_raw(NetClientState *nc, const uint8_t *buf, int size);
 ssize_t qemu_send_packet_async(NetClientState *nc, const uint8_t *buf,
                                int size, NetPacketSent *sent_cb);