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Date: Thu, 03 Mar 2011 08:55:01 +0100 From: Eric Dumazet <eric.dumazet@...il.com> To: Changli Gao <xiaosuo@...il.com> Cc: Jay Vosburgh <fubar@...ibm.com>, "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org Subject: Re: [PATCH 2/2 v2] bonding: COW before overwriting the destination MAC address Le jeudi 03 mars 2011 à 15:07 +0800, Changli Gao a écrit : > When there is a ptype handler holding a clone of this skb, whose > destination MAC addresse is overwritten, the owner of this handler may > get a corrupted packet. > > Signed-off-by: Changli Gao <xiaosuo@...il.com> > --- > v2: fix the bug in the previous one. Thank him. > drivers/net/bonding/bond_main.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c > index 912b416..7b7ca97 100644 > --- a/drivers/net/bonding/bond_main.c > +++ b/drivers/net/bonding/bond_main.c > @@ -1511,9 +1511,13 @@ static struct sk_buff *bond_handle_frame(struct sk_buff *skb) > if (bond_dev->priv_flags & IFF_MASTER_ALB && > bond_dev->priv_flags & IFF_BRIDGE_PORT && > skb->pkt_type == PACKET_HOST) { > - u16 *dest = (u16 *) eth_hdr(skb)->h_dest; > > - memcpy(dest, bond_dev->dev_addr, ETH_ALEN); > + if (unlikely(skb_cow_head(skb, > + skb->data - skb_mac_header(skb)))) { > + kfree_skb(skb); > + return NULL; > + } > + memcpy(eth_hdr(skb)->h_dest, bond_dev->dev_addr, ETH_ALEN); > } > > return skb; Thats minor, but using : u16 *dest = eth_hdr(skb)->h_dest; memcpy(dest, ptr, ETH_ALEN); Is better because compiler knows both destination and source are at least aligned on shorts. On some arches, it helps to not using 6 bytes copy, but 3 shorts. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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