Re: 2.6.32-rc5-git3: Reported regressions from 2.6.31

[Michael Buesch <mb@bu3sch.de>]

On Monday 26 October 2009 20:37:33 Michael Buesch wrote:
> Ok, it just turns out this actually is a driver bug.
> Thanks to Johannes Berg for tracking it down.
> 
> I think it's caused by the DMA bouncebuffer stuff that does not copy the skb->cb
> and does not adjust the "tx-info" pointer.
> I wonder why this didn't blow up easlier, because this bug is there since mac80211
> switched to using the CB.
> 
> Here's a completely untested patch.

Here's a new version of the patch that also fixes queue mapping bugs:

---
 drivers/net/wireless/b43/dma.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

--- wireless-testing.orig/drivers/net/wireless/b43/dma.c
+++ wireless-testing/drivers/net/wireless/b43/dma.c
@@ -1157,8 +1157,9 @@ struct b43_dmaring *parse_cookie(struct 
 }
 
 static int dma_tx_fragment(struct b43_dmaring *ring,
-			   struct sk_buff *skb)
+			   struct sk_buff **in_skb)
 {
+	struct sk_buff *skb = *in_skb;
 	const struct b43_dma_ops *ops = ring->ops;
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 	u8 *header;
@@ -1224,8 +1225,14 @@ static int dma_tx_fragment(struct b43_dm
 		}
 
 		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);
 		if (b43_dma_mapping_error(ring, meta->dmaaddr, skb->len, 1)) {
@@ -1355,7 +1362,11 @@ int b43_dma_tx(struct b43_wldev *dev, st
 	 * static, so we don't need to store it per frame. */
 	ring->queue_prio = skb_get_queue_mapping(skb);
 
-	err = dma_tx_fragment(ring, 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);
 	if (unlikely(err == -ENOKEY)) {
 		/* Drop this packet, as we don't have the encryption key
 		 * anymore and must not transmit it unencrypted. */



-- 
Greetings, Michael.