gianfar: fix BUG under load after introduction of skb recycling
Since commit 0fd56bb5be6455d0d42241e65aed057244665e5e ("gianfar:
Add support for skb recycling"), gianfar puts skbuffs that are in
the rx ring back onto the recycle list as-is in case there was a
receive error, but this breaks the following invariant: that all
skbuffs on the recycle list have skb->data = skb->head + NET_SKB_PAD.
The RXBUF_ALIGNMENT realignment done in gfar_new_skb() will be done
twice on skbuffs recycled in this way, causing there not to be enough
room in the skb anymore to receive a full packet, eventually leading
to an skb_over_panic from gfar_clean_rx_ring() -> skb_put().
Resetting the skb->data pointer to skb->head + NET_SKB_PAD before
putting the skb back onto the recycle list restores the mentioned
invariant, and should fix this issue.
Reported-by: Michael Guntsche <mike@it-loops.com>
Tested-by: Michael Guntsche <mike@it-loops.com>
Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c
index b2c4967..a051918 100644
--- a/drivers/net/gianfar.c
+++ b/drivers/net/gianfar.c
@@ -1885,8 +1885,17 @@
if (unlikely(!newskb))
newskb = skb;
- else if (skb)
+ else if (skb) {
+ /*
+ * We need to reset ->data to what it
+ * was before gfar_new_skb() re-aligned
+ * it to an RXBUF_ALIGNMENT boundary
+ * before we put the skb back on the
+ * recycle list.
+ */
+ skb->data = skb->head + NET_SKB_PAD;
__skb_queue_head(&priv->rx_recycle, skb);
+ }
} else {
/* Increment the number of packets */
dev->stats.rx_packets++;