Commit 069f40fc authored Apr 20, 2011 by Stanislaw Gruszka Committed by John W. Linville Apr 20, 2011

iwl4965: fix skb usage after free



Since

commit a120e912
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>

parent b2502698

drivers/net/wireless/iwlegacy/iwl-4965-tx.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -1127,12 +1127,16 @@ int iwl4965_tx_queue_reclaim(struct iwl_priv *priv, int txq_id, int index)
		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);