cfg80211: fix BSS struct IE access races

When a BSS struct is updated, the IEs are currently
overwritten or freed. This can lead to races if some
other CPU is accessing the BSS struct and using the
IEs concurrently.

Fix this by always allocating the IEs in a new struct
that holds the data and length and protecting access
to this new struct with RCU.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 26 insertions, 9 deletions

diff --git a/drivers/net/wireless/mwifiex/sta_ioctl.c b/drivers/net/wireless/mwifiex/sta_ioctl.c
index 24af6ba7d8a1..5d7b83e2dc4d 100644
--- a/drivers/net/wireless/mwifiex/sta_ioctl.c
+++ b/drivers/net/wireless/mwifiex/sta_ioctl.c
@@ -158,12 +158,22 @@ int mwifiex_fill_new_bss_desc(struct mwifiex_private *priv,
                               struct cfg80211_bss *bss,
                               struct mwifiex_bssdescriptor *bss_desc)
 {
-        int ret;
+        int ret, beacon_ie_len;
         u8 *beacon_ie;
         struct mwifiex_bss_priv *bss_priv = (void *)bss->priv;
+        const struct cfg80211_bss_ies *ies;
+
+        rcu_read_lock();
+        ies = rcu_dereference(bss->ies);
+        if (WARN_ON(!ies)) {
+                /* should never happen */
+                rcu_read_unlock();
+                return -EINVAL;
+        }
+        beacon_ie = kmemdup(ies->data, ies->len, GFP_ATOMIC);
+        beacon_ie_len = ies->len;
+        rcu_read_unlock();
 
-        beacon_ie = kmemdup(bss->information_elements, bss->len_beacon_ies,
-                            GFP_KERNEL);
         if (!beacon_ie) {
                 dev_err(priv->adapter->dev, " failed to alloc beacon_ie\n");
                 return -ENOMEM;
@@ -172,7 +182,7 @@ int mwifiex_fill_new_bss_desc(struct mwifiex_private *priv,
         memcpy(bss_desc->mac_address, bss->bssid, ETH_ALEN);
         bss_desc->rssi = bss->signal;
         bss_desc->beacon_buf = beacon_ie;
-        bss_desc->beacon_buf_size = bss->len_beacon_ies;
+        bss_desc->beacon_buf_size = beacon_ie_len;
         bss_desc->beacon_period = bss->beacon_interval;
         bss_desc->cap_info_bitmap = bss->capability;
         bss_desc->bss_band = bss_priv->band;
@@ -198,18 +208,23 @@ int mwifiex_fill_new_bss_desc(struct mwifiex_private *priv,
 static int mwifiex_process_country_ie(struct mwifiex_private *priv,
                                       struct cfg80211_bss *bss)
 {
-        u8 *country_ie, country_ie_len;
+        const u8 *country_ie;
+        u8 country_ie_len;
         struct mwifiex_802_11d_domain_reg *domain_info =
                                         &priv->adapter->domain_reg;
 
-        country_ie = (u8 *)ieee80211_bss_get_ie(bss, WLAN_EID_COUNTRY);
-
-        if (!country_ie)
+        rcu_read_lock();
+        country_ie = ieee80211_bss_get_ie(bss, WLAN_EID_COUNTRY);
+        if (!country_ie) {
+                rcu_read_unlock();
                 return 0;
+        }
 
         country_ie_len = country_ie[1];
-        if (country_ie_len < IEEE80211_COUNTRY_IE_MIN_LEN)
+        if (country_ie_len < IEEE80211_COUNTRY_IE_MIN_LEN) {
+                rcu_read_unlock();
                 return 0;
+        }
 
         domain_info->country_code[0] = country_ie[2];
         domain_info->country_code[1] = country_ie[3];
@@ -223,6 +238,8 @@ static int mwifiex_process_country_ie(struct mwifiex_private *priv,
         memcpy((u8 *)domain_info->triplet,
                &country_ie[2] + IEEE80211_COUNTRY_STRING_LEN, country_ie_len);
 
+        rcu_read_unlock();
+
         if (mwifiex_send_cmd_async(priv, HostCmd_CMD_802_11D_DOMAIN_INFO,
                                    HostCmd_ACT_GEN_SET, 0, NULL)) {
                 wiphy_err(priv->adapter->wiphy,