We should only tell the hardware its capable of DMA'ing
to us only what we asked dev_alloc_skb(). Prior to this
it is possible a large RX'd frame could have corrupted
DMA data but for us but we were saved only because we
were previously also pci_map_single()'ing the same large
value. The issue prior to this though was we were unmapping
a smaller amount which the prior DMA patch fixed.
Note that we dev_alloc_skb() a cache line size - 1 too
but this is just to help us offset the skb->data *if and only if*
needed. Even in that case we should still *only* allow the
hardware to DMA to us a buffer of size sc->sc_rxbufsize.
Signed-off-by: Luis R. Rodriguez <lrodriguez@xxxxxxxxxxx>
---
drivers/net/wireless/ath9k/recv.c | 13 +++++++++++--
1 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/net/wireless/ath9k/recv.c b/drivers/net/wireless/ath9k/recv.c
index 4355c16..0cd2a91 100644
--- a/drivers/net/wireless/ath9k/recv.c
+++ b/drivers/net/wireless/ath9k/recv.c
@@ -41,9 +41,11 @@ static void ath_rx_buf_link(struct ath_softc *sc, struct ath_buf *bf)
ASSERT(skb != NULL);
ds->ds_vdata = skb->data;
- /* setup rx descriptors */
+ /* setup rx descriptors. The sc_rxbufsize here tells the harware
+ * how much data it can DMA to us and that we are prepared
+ * to process */
ath9k_hw_setuprxdesc(ah, ds,
- skb_tailroom(skb), /* buffer size */
+ sc->sc_rxbufsize,
0);
if (sc->sc_rxlink == NULL)
@@ -66,6 +68,13 @@ static struct sk_buff *ath_rxbuf_alloc(struct ath_softc *sc, u32 len)
* in rx'd frames.
*/
+ /* Note: the kernel can allocate a value greater than
+ * what we ask it to give us. We really only need 4 KB as that
+ * is this hardware supports and in fact we need at least 3849
+ * as that is the MAX AMSDU size this hardware supports.
+ * Unfortunately this means we may get 8 KB here from the
+ * kernel... and that is actually what is observed on some
+ * systems :( */
skb = dev_alloc_skb(len + sc->sc_cachelsz - 1);
if (skb != NULL) {
off = ((unsigned long) skb->data) % sc->sc_cachelsz;
--
1.5.6.rc2.15.g457bb.dirty
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