From 4e2fd555199977c5994d1a4d2d3b8761b20ca4c7 Mon Sep 17 00:00:00 2001 From: Lennert Buytenhek Date: Mon, 25 May 2009 00:42:34 -0700 Subject: [PATCH] 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 Tested-by: Michael Guntsche Signed-off-by: Lennert Buytenhek Signed-off-by: David S. Miller --- drivers/net/gianfar.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c index b2c49679bba7..a0519184e54e 100644 --- a/drivers/net/gianfar.c +++ b/drivers/net/gianfar.c @@ -1885,8 +1885,17 @@ int gfar_clean_rx_ring(struct net_device *dev, int rx_work_limit) 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++; -- 2.20.1