mwifiex: fix tx_info/rx_info overlap with PCIe dma_mapping

On PCIe Tx data path, network interface specific tx_info
parameters such as bss_num and bss_type are saved at
"skb->cb + sizeof(dma_addr_t)" (returned by MWIFIEX_SKB_TXCB).
Later mwifiex_map_pci_memory() called from
mwifiex_pcie_send_data() will memcpy
sizeof(struct mwifiex_dma_mapping) bytes to save PCIe DMA
address and length information at beginning of skb->cb.
This accidently overwrites bss_num and bss_type saved in skb->cb
previously because bss_num/bss_type and mwifiex_dma_mapping data
overlap.
Similarly, on PCIe Rx data path, rx_info parameters overlaps
with PCIe DMA address and length information too.

Fix it by defining mwifiex_cb structure and having
MWIFIEX_SKB_TXCB and MWIFIEX_SKB_RXCB return the correct address
of tx_info/rx_info using the structure members.

Also add a BUILD_BUG_ON to maks sure that mwifiex_cb structure
doesn't exceed the size of skb->cb.

Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Signed-off-by: Chin-Ran Lo <crlo@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 35 insertions, 12 deletions

diff --git a/drivers/net/wireless/mwifiex/pcie.c b/drivers/net/wireless/mwifiex/pcie.c
index 574d4b597468..2cc9b6fca490 100644
--- a/drivers/net/wireless/mwifiex/pcie.c
+++ b/drivers/net/wireless/mwifiex/pcie.c
@@ -50,7 +50,7 @@ mwifiex_map_pci_memory(struct mwifiex_adapter *adapter, struct sk_buff *skb,
                 return -1;
         }
         mapping.len = size;
-        memcpy(skb->cb, &mapping, sizeof(mapping));
+        mwifiex_store_mapping(skb, &mapping);
         return 0;
 }
 
@@ -60,7 +60,7 @@ static void mwifiex_unmap_pci_memory(struct mwifiex_adapter *adapter,
         struct pcie_service_card *card = adapter->card;
         struct mwifiex_dma_mapping mapping;
 
-        MWIFIEX_SKB_PACB(skb, &mapping);
+        mwifiex_get_mapping(skb, &mapping);
         pci_unmap_single(card->dev, mapping.addr, mapping.len, flags);
 }
 
diff --git a/drivers/net/wireless/mwifiex/util.h b/drivers/net/wireless/mwifiex/util.h
index ddae57021397..caadb3737b9e 100644
--- a/drivers/net/wireless/mwifiex/util.h
+++ b/drivers/net/wireless/mwifiex/util.h
@@ -20,32 +20,55 @@
 #ifndef _MWIFIEX_UTIL_H_
 #define _MWIFIEX_UTIL_H_
 
+struct mwifiex_dma_mapping {
+        dma_addr_t addr;
+        size_t len;
+};
+
+struct mwifiex_cb {
+        struct mwifiex_dma_mapping dma_mapping;
+        union {
+                struct mwifiex_rxinfo rx_info;
+                struct mwifiex_txinfo tx_info;
+        };
+};
+
 static inline struct mwifiex_rxinfo *MWIFIEX_SKB_RXCB(struct sk_buff *skb)
 {
-        return (struct mwifiex_rxinfo *)(skb->cb + sizeof(dma_addr_t));
+        struct mwifiex_cb *cb = (struct mwifiex_cb *)skb->cb;
+
+        BUILD_BUG_ON(sizeof(struct mwifiex_cb) > sizeof(skb->cb));
+        return &cb->rx_info;
 }
 
 static inline struct mwifiex_txinfo *MWIFIEX_SKB_TXCB(struct sk_buff *skb)
 {
-        return (struct mwifiex_txinfo *)(skb->cb + sizeof(dma_addr_t));
+        struct mwifiex_cb *cb = (struct mwifiex_cb *)skb->cb;
+
+        return &cb->tx_info;
 }
 
-struct mwifiex_dma_mapping {
-        dma_addr_t addr;
-        size_t len;
-};
+static inline void mwifiex_store_mapping(struct sk_buff *skb,
+                                         struct mwifiex_dma_mapping *mapping)
+{
+        struct mwifiex_cb *cb = (struct mwifiex_cb *)skb->cb;
+
+        memcpy(&cb->dma_mapping, mapping, sizeof(*mapping));
+}
 
-static inline void MWIFIEX_SKB_PACB(struct sk_buff *skb,
-                                        struct mwifiex_dma_mapping *mapping)
+static inline void mwifiex_get_mapping(struct sk_buff *skb,
+                                       struct mwifiex_dma_mapping *mapping)
 {
-        memcpy(mapping, skb->cb, sizeof(*mapping));
+        struct mwifiex_cb *cb = (struct mwifiex_cb *)skb->cb;
+
+        memcpy(mapping, &cb->dma_mapping, sizeof(*mapping));
 }
 
 static inline dma_addr_t MWIFIEX_SKB_DMA_ADDR(struct sk_buff *skb)
 {
         struct mwifiex_dma_mapping mapping;
 
-        MWIFIEX_SKB_PACB(skb, &mapping);
+        mwifiex_get_mapping(skb, &mapping);
 
         return mapping.addr;
 }