p54pci: rx frame length check

A long time ago, a user reported several crashes due to
data corruptions which are likely the result of a
not-100%-supported, or faulty? PCI bridge.
( http://patchwork.kernel.org/patch/53004/ )

This patch fixes entry #1.
"1.  p54p_check_rx_ring - skb_over_panic: Under a ping flood
or just left running for a bit would panic with a skb_over_panic."
As described in the mail: The invalid frame length causes
skb_put to bailout and trigger a crash.

Note:
Simply dropping the frame is problematic, because if its content
contains a tx feedback we would lose some portion of the device
memory space.... And the driver/mac80211 should handle all other
invalid data.

Reported-by: Quintin Pitts <geek4linux@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/net/wireless/p54/p54pci.c b/drivers/net/wireless/p54/p54pci.c
index a15962a19b2a..a72f7c2577de 100644
--- a/drivers/net/wireless/p54/p54pci.c
+++ b/drivers/net/wireless/p54/p54pci.c
@@ -197,6 +197,14 @@ static void p54p_check_rx_ring(struct ieee80211_hw *dev, u32 *index,
                         i %= ring_limit;
                         continue;
                 }
+
+                if (unlikely(len > priv->common.rx_mtu)) {
+                        if (net_ratelimit())
+                                dev_err(&priv->pdev->dev, "rx'd frame size "
+                                        "exceeds length threshold.\n");
+
+                        len = priv->common.rx_mtu;
+                }
                 skb_put(skb, len);
 
                 if (p54_rx(dev, skb)) {