rtlwifi: Fix error when accessing unmapped memory in skb

These drivers use 9100-byte receive buffers, thus allocating an skb requires
an O(3) memory allocation. Under heavy memory loads and fragmentation, such
a request can fail. Previous versions of the driver have dropped the packet
and reused the old buffer; however, the new version introduced a bug in that
it released the old buffer before trying to allocate a new one. The previous
method is implemented here. The skb is unmapped before any attempt is made to
allocate another.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@vger.kernel.org>  [v3.18]
Reported-by: Eric Biggers <ebiggers3@gmail.com>
Cc: Eric Biggers <ebiggers3@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

1 files changed, 24 insertions, 8 deletions

diff --git a/drivers/net/wireless/rtlwifi/pci.c b/drivers/net/wireless/rtlwifi/pci.c
index 846a2e6e34d8..c70efb9a6e78 100644
--- a/drivers/net/wireless/rtlwifi/pci.c
+++ b/drivers/net/wireless/rtlwifi/pci.c
@@ -666,7 +666,8 @@ tx_status_ok:
 }
 
 static int _rtl_pci_init_one_rxdesc(struct ieee80211_hw *hw,
-                                    u8 *entry, int rxring_idx, int desc_idx)
+                                    struct sk_buff *new_skb, u8 *entry,
+                                    int rxring_idx, int desc_idx)
 {
         struct rtl_priv *rtlpriv = rtl_priv(hw);
         struct rtl_pci *rtlpci = rtl_pcidev(rtl_pcipriv(hw));
@@ -674,11 +675,15 @@ static int _rtl_pci_init_one_rxdesc(struct ieee80211_hw *hw,
         u8 tmp_one = 1;
         struct sk_buff *skb;
 
+        if (likely(new_skb)) {
+                skb = new_skb;
+                goto remap;
+        }
         skb = dev_alloc_skb(rtlpci->rxbuffersize);
         if (!skb)
                 return 0;
-        rtlpci->rx_ring[rxring_idx].rx_buf[desc_idx] = skb;
 
+remap:
         /* just set skb->cb to mapping addr for pci_unmap_single use */
         *((dma_addr_t *)skb->cb) =
                 pci_map_single(rtlpci->pdev, skb_tail_pointer(skb),
@@ -686,6 +691,7 @@ static int _rtl_pci_init_one_rxdesc(struct ieee80211_hw *hw,
         bufferaddress = *((dma_addr_t *)skb->cb);
         if (pci_dma_mapping_error(rtlpci->pdev, bufferaddress))
                 return 0;
+        rtlpci->rx_ring[rxring_idx].rx_buf[desc_idx] = skb;
         if (rtlpriv->use_new_trx_flow) {
                 rtlpriv->cfg->ops->set_desc(hw, (u8 *)entry, false,
                                             HW_DESC_RX_PREPARE,
@@ -781,6 +787,7 @@ static void _rtl_pci_rx_interrupt(struct ieee80211_hw *hw)
                 /*rx pkt */
                 struct sk_buff *skb = rtlpci->rx_ring[rxring_idx].rx_buf[
                                       rtlpci->rx_ring[rxring_idx].idx];
+                struct sk_buff *new_skb;
 
                 if (rtlpriv->use_new_trx_flow) {
                         rx_remained_cnt =
@@ -807,6 +814,13 @@ static void _rtl_pci_rx_interrupt(struct ieee80211_hw *hw)
                 pci_unmap_single(rtlpci->pdev, *((dma_addr_t *)skb->cb),
                                  rtlpci->rxbuffersize, PCI_DMA_FROMDEVICE);
 
+                /* get a new skb - if fail, old one will be reused */
+                new_skb = dev_alloc_skb(rtlpci->rxbuffersize);
+                if (unlikely(!new_skb)) {
+                        pr_err("Allocation of new skb failed in %s\n",
+                               __func__);
+                        goto no_new;
+                }
                 if (rtlpriv->use_new_trx_flow) {
                         buffer_desc =
                           &rtlpci->rx_ring[rxring_idx].buffer_desc
@@ -911,14 +925,16 @@ static void _rtl_pci_rx_interrupt(struct ieee80211_hw *hw)
                         schedule_work(&rtlpriv->works.lps_change_work);
                 }
 end:
+                skb = new_skb;
+no_new:
                 if (rtlpriv->use_new_trx_flow) {
-                        _rtl_pci_init_one_rxdesc(hw, (u8 *)buffer_desc,
+                        _rtl_pci_init_one_rxdesc(hw, skb, (u8 *)buffer_desc,
                                                  rxring_idx,
-                                               rtlpci->rx_ring[rxring_idx].idx);
+                                                 rtlpci->rx_ring[rxring_idx].idx);
                 } else {
-                        _rtl_pci_init_one_rxdesc(hw, (u8 *)pdesc, rxring_idx,
+                        _rtl_pci_init_one_rxdesc(hw, skb, (u8 *)pdesc,
+                                                 rxring_idx,
                                                  rtlpci->rx_ring[rxring_idx].idx);
-
                         if (rtlpci->rx_ring[rxring_idx].idx ==
                             rtlpci->rxringcount - 1)
                                 rtlpriv->cfg->ops->set_desc(hw, (u8 *)pdesc,
@@ -1307,7 +1323,7 @@ static int _rtl_pci_init_rx_ring(struct ieee80211_hw *hw, int rxring_idx)
                 rtlpci->rx_ring[rxring_idx].idx = 0;
                 for (i = 0; i < rtlpci->rxringcount; i++) {
                         entry = &rtlpci->rx_ring[rxring_idx].buffer_desc[i];
-                        if (!_rtl_pci_init_one_rxdesc(hw, (u8 *)entry,
+                        if (!_rtl_pci_init_one_rxdesc(hw, NULL, (u8 *)entry,
                                                       rxring_idx, i))
                                 return -ENOMEM;
                 }
@@ -1332,7 +1348,7 @@ static int _rtl_pci_init_rx_ring(struct ieee80211_hw *hw, int rxring_idx)
 
                 for (i = 0; i < rtlpci->rxringcount; i++) {
                         entry = &rtlpci->rx_ring[rxring_idx].desc[i];
-                        if (!_rtl_pci_init_one_rxdesc(hw, (u8 *)entry,
+                        if (!_rtl_pci_init_one_rxdesc(hw, NULL, (u8 *)entry,
                                                       rxring_idx, i))
                                 return -ENOMEM;
                 }