iwlwifi: fix use after free bug for paged rx
In the paged rx patch (4854fde2), I introduced a bug that could possibly
touch an already freed page. It is fixed by avoiding the access in this
patch. I've also added some comments so that other people touching the
code won't make the same mistake. In the future, if we cannot avoid
access the page after being handled to the upper layer, we can use
get_page/put_page to handle it. For now, it's just not necessary.
It also fixed a debug message print bug reported by Stanislaw Gruszka
<sgruszka@redhat.com>.
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-3945.c b/drivers/net/wireless/iwlwifi/iwl-3945.c
index 269b988..f5d7528 100644
--- a/drivers/net/wireless/iwlwifi/iwl-3945.c
+++ b/drivers/net/wireless/iwlwifi/iwl-3945.c
@@ -548,6 +548,7 @@
u16 len = le16_to_cpu(rx_hdr->len);
struct sk_buff *skb;
int ret;
+ __le16 fc = hdr->frame_control;
/* We received data from the HW, so stop the watchdog */
if (unlikely(len + IWL39_RX_FRAME_SIZE >
@@ -580,9 +581,9 @@
/* mac80211 currently doesn't support paged SKB. Convert it to
* linear SKB for management frame and data frame requires
* software decryption or software defragementation. */
- if (ieee80211_is_mgmt(hdr->frame_control) ||
- ieee80211_has_protected(hdr->frame_control) ||
- ieee80211_has_morefrags(hdr->frame_control) ||
+ if (ieee80211_is_mgmt(fc) ||
+ ieee80211_has_protected(fc) ||
+ ieee80211_has_morefrags(fc) ||
le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_FRAG)
ret = skb_linearize(skb);
else
@@ -594,11 +595,15 @@
goto out;
}
- iwl_update_stats(priv, false, hdr->frame_control, len);
+ /*
+ * XXX: We cannot touch the page and its virtual memory (pkt) after
+ * here. It might have already been freed by the above skb change.
+ */
+ iwl_update_stats(priv, false, fc, len);
memcpy(IEEE80211_SKB_RXCB(skb), stats, sizeof(*stats));
- ieee80211_rx(priv->hw, skb);
+ ieee80211_rx(priv->hw, skb);
out:
priv->alloc_rxb_page--;
rxb->page = NULL;