rt2x00: Properly reserve room for descriptors in skbs.

Instead of fiddling with the skb->data pointer and thereby risking
out of bounds accesses, properly reserve the space needed in an
skb for descriptors.

Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>

1 files changed, 13 insertions, 9 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2800usb.c b/drivers/net/wireless/rt2x00/rt2800usb.c
index d0d8060040ba..ee407f138753 100644
--- a/drivers/net/wireless/rt2x00/rt2800usb.c
+++ b/drivers/net/wireless/rt2x00/rt2800usb.c
@@ -400,13 +400,14 @@ static void rt2800usb_write_tx_desc(struct rt2x00_dev *rt2x00dev,
                                     struct txentry_desc *txdesc)
 {
         struct skb_frame_desc *skbdesc = get_skb_frame_desc(skb);
-        __le32 *txi = (__le32 *)(skb->data - TXWI_DESC_SIZE - TXINFO_DESC_SIZE);
+        __le32 *txi = (__le32 *) skb->data;
+        __le32 *txwi = (__le32 *) (skb->data + TXINFO_DESC_SIZE);
         u32 word;
 
         /*
          * Initialize TXWI descriptor
          */
-        rt2800_write_txwi(skb, txdesc);
+        rt2800_write_txwi(txwi, txdesc);
 
         /*
          * Initialize TXINFO descriptor
@@ -426,6 +427,7 @@ static void rt2800usb_write_tx_desc(struct rt2x00_dev *rt2x00dev,
         /*
          * Register descriptor details in skb frame descriptor.
          */
+        skbdesc->flags |= SKBDESC_DESC_IN_SKB;
         skbdesc->desc = txi;
         skbdesc->desc_len = TXINFO_DESC_SIZE + TXWI_DESC_SIZE;
 }
@@ -450,15 +452,22 @@ static void rt2800usb_write_beacon(struct queue_entry *entry,
         rt2800_register_write(rt2x00dev, BCN_TIME_CFG, reg);
 
         /*
+         * Add space for the TXWI in front of the skb.
+         */
+        skb_push(entry->skb, TXWI_DESC_SIZE);
+        memset(entry->skb, 0, TXWI_DESC_SIZE);
+
+        /*
          * Register descriptor details in skb frame descriptor.
          */
-        skbdesc->desc = entry->skb->data - TXWI_DESC_SIZE;
+        skbdesc->flags |= SKBDESC_DESC_IN_SKB;
+        skbdesc->desc = entry->skb->data;
         skbdesc->desc_len = TXWI_DESC_SIZE;
 
         /*
          * Add the TXWI for the beacon to the skb.
          */
-        rt2800_write_txwi(entry->skb, txdesc);
+        rt2800_write_txwi((__le32 *) entry->skb->data, txdesc);
 
         /*
          * Dump beacon to userspace through debugfs.
@@ -466,11 +475,6 @@ static void rt2800usb_write_beacon(struct queue_entry *entry,
         rt2x00debug_dump_frame(rt2x00dev, DUMP_FRAME_BEACON, entry->skb);
 
         /*
-         * Adjust skb to take TXWI into account.
-         */
-        skb_push(entry->skb, TXWI_DESC_SIZE);
-
-        /*
          * Write entire beacon with descriptor to register.
          */
         beacon_base = HW_BEACON_OFFSET(entry->entry_idx);