b43: Rewrite TX bounce buffer handling

Do not mess with the original skb, but allocate an independent bouncebuffer.
This protects against bad interference with mac80211's assumptions about
the skb (which already caused bugs).
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/b43/dma.c

@@ -1157,18 +1157,17 @@ struct b43_dmaring *parse_cookie(struct b43_wldev *dev, u16 cookie, int *slot)
 }
 
 static int dma_tx_fragment(struct b43_dmaring *ring,
-			   struct sk_buff **in_skb)
+			   struct sk_buff *skb)
 {
-	struct sk_buff *skb = *in_skb;
 	const struct b43_dma_ops *ops = ring->ops;
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct b43_private_tx_info *priv_info = b43_get_priv_tx_info(info);
 	u8 *header;
 	int slot, old_top_slot, old_used_slots;
 	int err;
 	struct b43_dmadesc_generic *desc;
 	struct b43_dmadesc_meta *meta;
 	struct b43_dmadesc_meta *meta_hdr;
-	struct sk_buff *bounce_skb;
 	u16 cookie;
 	size_t hdrsize = b43_txhdr_size(ring->dev);
 
@@ -1212,34 +1211,28 @@ static int dma_tx_fragment(struct b43_dmaring *ring,
 
 	meta->skb = skb;
 	meta->is_last_fragment = 1;
+	priv_info->bouncebuffer = NULL;
 
 	meta->dmaaddr = map_descbuffer(ring, skb->data, skb->len, 1);
 	/* create a bounce buffer in zone_dma on mapping failure. */
 	if (b43_dma_mapping_error(ring, meta->dmaaddr, skb->len, 1)) {
-		bounce_skb = __dev_alloc_skb(skb->len, GFP_ATOMIC | GFP_DMA);
-		if (!bounce_skb) {
+		priv_info->bouncebuffer = kmalloc(skb->len, GFP_ATOMIC | GFP_DMA);
+		if (!priv_info->bouncebuffer) {
 			ring->current_slot = old_top_slot;
 			ring->used_slots = old_used_slots;
 			err = -ENOMEM;
 			goto out_unmap_hdr;
 		}
+		memcpy(priv_info->bouncebuffer, skb->data, skb->len);
 
-		memcpy(skb_put(bounce_skb, skb->len), skb->data, skb->len);
-		memcpy(bounce_skb->cb, skb->cb, sizeof(skb->cb));
-		bounce_skb->dev = skb->dev;
-		skb_set_queue_mapping(bounce_skb, skb_get_queue_mapping(skb));
-		info = IEEE80211_SKB_CB(bounce_skb);
-
-		dev_kfree_skb_any(skb);
-		skb = bounce_skb;
-		*in_skb = bounce_skb;
-		meta->skb = skb;
-		meta->dmaaddr = map_descbuffer(ring, skb->data, skb->len, 1);
+		meta->dmaaddr = map_descbuffer(ring, priv_info->bouncebuffer, skb->len, 1);
 		if (b43_dma_mapping_error(ring, meta->dmaaddr, skb->len, 1)) {
+			kfree(priv_info->bouncebuffer);
+			priv_info->bouncebuffer = NULL;
 			ring->current_slot = old_top_slot;
 			ring->used_slots = old_used_slots;
 			err = -EIO;
-			goto out_free_bounce;
+			goto out_unmap_hdr;
 		}
 	}
 
@@ -1256,8 +1249,6 @@ static int dma_tx_fragment(struct b43_dmaring *ring,
 	ops->poke_tx(ring, next_slot(ring, slot));
 	return 0;
 
-out_free_bounce:
-	dev_kfree_skb_any(skb);
 out_unmap_hdr:
 	unmap_descbuffer(ring, meta_hdr->dmaaddr,
 			 hdrsize, 1);
@@ -1362,11 +1353,7 @@ int b43_dma_tx(struct b43_wldev *dev, struct sk_buff *skb)
 	 * static, so we don't need to store it per frame. */
 	ring->queue_prio = skb_get_queue_mapping(skb);
 
-	/* dma_tx_fragment might reallocate the skb, so invalidate pointers pointing
-	 * into the skb data or cb now. */
-	hdr = NULL;
-	info = NULL;
-	err = dma_tx_fragment(ring, &skb);
+	err = dma_tx_fragment(ring, skb);
 	if (unlikely(err == -ENOKEY)) {
 		/* Drop this packet, as we don't have the encryption key
 		 * anymore and must not transmit it unencrypted. */
@@ -1413,12 +1400,17 @@ void b43_dma_handle_txstatus(struct b43_wldev *dev,
 		B43_WARN_ON(!(slot >= 0 && slot < ring->nr_slots));
 		desc = ops->idx2desc(ring, slot, &meta);
 
-		if (meta->skb)
-			unmap_descbuffer(ring, meta->dmaaddr, meta->skb->len,
-					 1);
-		else
+		if (meta->skb) {
+			struct b43_private_tx_info *priv_info =
+				b43_get_priv_tx_info(IEEE80211_SKB_CB(meta->skb));
+
+			unmap_descbuffer(ring, meta->dmaaddr, meta->skb->len, 1);
+			kfree(priv_info->bouncebuffer);
+			priv_info->bouncebuffer = NULL;
+		} else {
 			unmap_descbuffer(ring, meta->dmaaddr,
 					 b43_txhdr_size(dev), 1);
+		}
 
 		if (meta->is_last_fragment) {
 			struct ieee80211_tx_info *info;

drivers/net/wireless/b43/xmit.h

@@ -2,6 +2,8 @@
 #define B43_XMIT_H_
 
 #include "main.h"
+#include <net/mac80211.h>
+
 
 #define _b43_declare_plcp_hdr(size) \
 	struct b43_plcp_hdr##size {		\
@@ -332,4 +334,21 @@ static inline u8 b43_kidx_to_raw(struct b43_wldev *dev, u8 firmware_kidx)
 	return raw_kidx;
 }
 
+/* struct b43_private_tx_info - TX info private to b43.
+ * The structure is placed in (struct ieee80211_tx_info *)->rate_driver_data
+ *
+ * @bouncebuffer: DMA Bouncebuffer (if used)
+ */
+struct b43_private_tx_info {
+	void *bouncebuffer;
+};
+
+static inline struct b43_private_tx_info *
+b43_get_priv_tx_info(struct ieee80211_tx_info *info)
+{
+	BUILD_BUG_ON(sizeof(struct b43_private_tx_info) >
+		     sizeof(info->rate_driver_data));
+	return (struct b43_private_tx_info *)info->rate_driver_data;
+}
+
 #endif /* B43_XMIT_H_ */