iwl4965: fix skb usage after free
Since
commit a120e912eb51e347f36c71b60a1d13af74d30e83
Author: Stanislaw Gruszka <sgruszka@redhat.com>
Date: Fri Feb 19 15:47:33 2010 -0800
iwlwifi: sanity check before counting number of tfds can be free
we use skb->data after calling ieee80211_tx_status_irqsafe(), which
could free skb instantly.
On current kernels I do not observe practical problems related with
bug, but on 2.6.35.y it cause random system hangs when stressing
wireless link, making bisection of other problems impossible.
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlegacy/iwl-4965-tx.c b/drivers/net/wireless/iwlegacy/iwl-4965-tx.c
index 5c40502..fbec88d 100644
--- a/drivers/net/wireless/iwlegacy/iwl-4965-tx.c
+++ b/drivers/net/wireless/iwlegacy/iwl-4965-tx.c
@@ -1127,12 +1127,16 @@
q->read_ptr = iwl_legacy_queue_inc_wrap(q->read_ptr, q->n_bd)) {
tx_info = &txq->txb[txq->q.read_ptr];
- iwl4965_tx_status(priv, tx_info,
- txq_id >= IWL4965_FIRST_AMPDU_QUEUE);
+
+ if (WARN_ON_ONCE(tx_info->skb == NULL))
+ continue;
hdr = (struct ieee80211_hdr *)tx_info->skb->data;
- if (hdr && ieee80211_is_data_qos(hdr->frame_control))
+ if (ieee80211_is_data_qos(hdr->frame_control))
nfreed++;
+
+ iwl4965_tx_status(priv, tx_info,
+ txq_id >= IWL4965_FIRST_AMPDU_QUEUE);
tx_info->skb = NULL;
priv->cfg->ops->lib->txq_free_tfd(priv, txq);
