iwlagn: fix NULL ptr deref when reprogramming sta w/o LQ

Reinette reports a crash in iwl_reprogram_ap_sta(). The
debugging shows:

  b1 16    mov    $0x16,%cl
 *f3 a5    rep movsl %ds     <-- trapping instruction:(%rsi),%es:(%rdi)

which is a memcpy of 22 (0x16) words (movsl). this points
to "priv->stations[sta_id].lq" being NULL since that is
the memcpy() of that size here.

The only way I see for this to happen is if we try to
do some RXON reprogramming while connecting to an AP,
after tx_sync() but before full setup, but that seems
like something that might very well happen.

Fix this by checking if the LQ is present and only then
reprogramming it.

Reported-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-agn-sta.c b/drivers/net/wireless/iwlwifi/iwl-agn-sta.c
index 93067686218..1b112dfbce7 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn-sta.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn-sta.c
@@ -647,7 +647,7 @@ void iwl_reprogram_ap_sta(struct iwl_priv *priv, struct iwl_rxon_context *ctx)
         int ret;
         struct iwl_addsta_cmd sta_cmd;
         struct iwl_link_quality_cmd lq;
-        bool active;
+        bool active, have_lq = false;
 
         spin_lock_irqsave(&priv->shrd->sta_lock, flags);
         if (!(priv->stations[sta_id].used & IWL_STA_DRIVER_ACTIVE)) {
@@ -657,7 +657,10 @@ void iwl_reprogram_ap_sta(struct iwl_priv *priv, struct iwl_rxon_context *ctx)
 
         memcpy(&sta_cmd, &priv->stations[sta_id].sta, sizeof(sta_cmd));
         sta_cmd.mode = 0;
-        memcpy(&lq, priv->stations[sta_id].lq, sizeof(lq));
+        if (priv->stations[sta_id].lq) {
+                memcpy(&lq, priv->stations[sta_id].lq, sizeof(lq));
+                have_lq = true;
+        }
 
         active = priv->stations[sta_id].used & IWL_STA_UCODE_ACTIVE;
         priv->stations[sta_id].used &= ~IWL_STA_DRIVER_ACTIVE;
@@ -679,7 +682,8 @@ void iwl_reprogram_ap_sta(struct iwl_priv *priv, struct iwl_rxon_context *ctx)
         if (ret)
                 IWL_ERR(priv, "failed to re-add STA %pM (%d)\n",
                         priv->stations[sta_id].sta.sta.addr, ret);
-        iwl_send_lq_cmd(priv, ctx, &lq, CMD_SYNC, true);
+        if (have_lq)
+                iwl_send_lq_cmd(priv, ctx, &lq, CMD_SYNC, true);
 }
 
 int iwl_get_free_ucode_key_offset(struct iwl_priv *priv)