mac80211: split ieee80211_key_alloc/free

In order to RCU-ify sta_info, we need to be able to allocate
a key without linking it to an sdata/sta structure (because
allocation cannot be done in an rcu critical section). This
patch splits up ieee80211_key_alloc() and updates all users
appropriately.

While at it, this patch fixes a number of race conditions
such as finally making key replacement atomic, unfortunately
at the expense of more complex code.

Note that this patch documents /existing/ bugs with sta info
and key interaction, there is currently a race condition
when a sta info is freed without holding the RTNL. This will
finally be fixed by a followup patch.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 48 insertions, 42 deletions

diff --git a/net/mac80211/ieee80211_ioctl.c b/net/mac80211/ieee80211_ioctl.c
index 54ad07aafe2d..7551db3f3abc 100644
--- a/net/mac80211/ieee80211_ioctl.c
+++ b/net/mac80211/ieee80211_ioctl.c
@@ -33,8 +33,8 @@ static int ieee80211_set_encryption(struct net_device *dev, u8 *sta_addr,
                                     size_t key_len)
 {
         struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
-        int ret = 0;
-        struct sta_info *sta;
+        int ret;
+        struct sta_info *sta = NULL;
         struct ieee80211_key *key;
         struct ieee80211_sub_if_data *sdata;
 
@@ -46,58 +46,64 @@ static int ieee80211_set_encryption(struct net_device *dev, u8 *sta_addr,
                 return -EINVAL;
         }
 
-        if (is_broadcast_ether_addr(sta_addr)) {
-                sta = NULL;
-                key = sdata->keys[idx];
-        } else {
-                set_tx_key = 0;
-                /*
-                 * According to the standard, the key index of a pairwise
-                 * key must be zero. However, some AP are broken when it
-                 * comes to WEP key indices, so we work around this.
-                 */
-                if (idx != 0 && alg != ALG_WEP) {
-                        printk(KERN_DEBUG "%s: set_encrypt - non-zero idx for "
-                               "individual key\n", dev->name);
-                        return -EINVAL;
+        if (remove) {
+                if (is_broadcast_ether_addr(sta_addr)) {
+                        key = sdata->keys[idx];
+                } else {
+                        sta = sta_info_get(local, sta_addr);
+                        if (!sta) {
+                                ret = -ENOENT;
+                                key = NULL;
+                                goto err_out;
+                        }
+
+                        key = sta->key;
                 }
 
-                sta = sta_info_get(local, sta_addr);
-                if (!sta) {
-#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
-                        DECLARE_MAC_BUF(mac);
-                        printk(KERN_DEBUG "%s: set_encrypt - unknown addr "
-                               "%s\n",
-                               dev->name, print_mac(mac, sta_addr));
-#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
+                if (!key)
+                        ret = -ENOENT;
+                else
+                        ret = 0;
+        } else {
+                key = ieee80211_key_alloc(alg, idx, key_len, _key);
+                if (!key)
+                        return -ENOMEM;
+
+                if (!is_broadcast_ether_addr(sta_addr)) {
+                        set_tx_key = 0;
+                        /*
+                         * According to the standard, the key index of a
+                         * pairwise key must be zero. However, some AP are
+                         * broken when it comes to WEP key indices, so we
+                         * work around this.
+                         */
+                        if (idx != 0 && alg != ALG_WEP) {
+                                ret = -EINVAL;
+                                goto err_out;
+                        }
 
-                        return -ENOENT;
+                        sta = sta_info_get(local, sta_addr);
+                        if (!sta) {
+                                ret = -ENOENT;
+                                goto err_out;
+                        }
                 }
 
-                key = sta->key;
-        }
+                ieee80211_key_link(key, sdata, sta);
 
-        if (remove) {
-                ieee80211_key_free(key);
+                if (set_tx_key || (!sta && !sdata->default_key && key))
+                        ieee80211_set_default_key(sdata, idx);
+
+                /* don't free key later */
                 key = NULL;
-        } else {
-                /*
-                 * Automatically frees any old key if present.
-                 */
-                key = ieee80211_key_alloc(sdata, sta, alg, idx, key_len, _key);
-                if (!key) {
-                        ret = -ENOMEM;
-                        goto err_out;
-                }
-        }
 
-        if (set_tx_key || (!sta && !sdata->default_key && key))
-                ieee80211_set_default_key(sdata, idx);
+                ret = 0;
+        }
 
-        ret = 0;
  err_out:
         if (sta)
                 sta_info_put(sta);
+        ieee80211_key_free(key);
         return ret;
 }