mwifiex: fix memory corruption when unsetting multicast list

When trying to unset a previously-set multicast list (i.e. the new list
has 0 entries), mwifiex_set_multicast_list() was calling down to
mwifiex_request_set_multicast_list() while leaving
mcast_list.num_multicast_addr as an uninitialized value.

We were arriving at mwifiex_cmd_mac_multicast_adr() which would then
proceed to do an often huge memcpy of
mcast_list.num_multicast_addr*ETH_ALEN bytes, causing memory corruption
and hard to debug crashes.

Fix this by setting mcast_list.num_multicast_addr to 0 when no multicast
list is provided. Similarly, fix up the logic in
mwifiex_request_set_multicast_list() to unset the multicast list that
was previously sent to the hardware in such cases.

Signed-off-by: Daniel Drake <dsd@laptop.org>
Acked-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 8 insertions, 10 deletions

diff --git a/drivers/net/wireless/mwifiex/sta_ioctl.c b/drivers/net/wireless/mwifiex/sta_ioctl.c
index 1a8a19dbd635..23aa910bc5d0 100644
--- a/drivers/net/wireless/mwifiex/sta_ioctl.c
+++ b/drivers/net/wireless/mwifiex/sta_ioctl.c
@@ -104,16 +104,14 @@ int mwifiex_request_set_multicast_list(struct mwifiex_private *priv,
                 } else {
                         priv->curr_pkt_filter &=
                                 ~HostCmd_ACT_MAC_ALL_MULTICAST_ENABLE;
-                        if (mcast_list->num_multicast_addr) {
-                                dev_dbg(priv->adapter->dev,
-                                        "info: Set multicast list=%d\n",
-                                       mcast_list->num_multicast_addr);
-                                /* Send multicast addresses to firmware */
-                                ret = mwifiex_send_cmd_async(priv,
-                                        HostCmd_CMD_MAC_MULTICAST_ADR,
-                                        HostCmd_ACT_GEN_SET, 0,
-                                        mcast_list);
-                        }
+                        dev_dbg(priv->adapter->dev,
+                                "info: Set multicast list=%d\n",
+                                mcast_list->num_multicast_addr);
+                        /* Send multicast addresses to firmware */
+                        ret = mwifiex_send_cmd_async(priv,
+                                HostCmd_CMD_MAC_MULTICAST_ADR,
+                                HostCmd_ACT_GEN_SET, 0,
+                                mcast_list);
                 }
         }
         dev_dbg(priv->adapter->dev,