From 5ff8dda3035d95df5bf6979136eb82b0e301726b Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Thu, 4 Jun 2009 01:22:01 +0000 Subject: [PATCH] net: Ensure partial checksum offset is inside the skb head On Thu, Jun 04, 2009 at 09:06:00PM +1000, Herbert Xu wrote: > > tun: Optimise handling of bogus gso->hdr_len > > As all current versions of virtio_net generate a value for the > header length that's too small, we should optimise this so that > we don't copy it twice. This can be done by ensuring that it is > at least as large as the place where we'll write the checksum. > > Signed-off-by: Herbert Xu With this applied we can strengthen the partial checksum check: In skb_partial_csum_set we check to see if the checksum offset is within the packet. However, we really should check that it is within the skb head as that's the only bit we can modify without copying. Signed-off-by: Herbert Xu Acked-by: Rusty Russell Signed-off-by: David S. Miller --- net/core/skbuff.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 6adf19ec95cc..a2473b1600e3 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3026,12 +3026,12 @@ EXPORT_SYMBOL_GPL(skb_tstamp_tx); */ bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off) { - if (unlikely(start > skb->len - 2) || - unlikely((int)start + off > skb->len - 2)) { + if (unlikely(start > skb_headlen(skb)) || + unlikely((int)start + off > skb_headlen(skb) - 2)) { if (net_ratelimit()) printk(KERN_WARNING "bad partial csum: csum=%u/%u len=%u\n", - start, off, skb->len); + start, off, skb_headlen(skb)); return false; } skb->ip_summed = CHECKSUM_PARTIAL; -- 2.30.2