Commit 15f35d49 authored Feb 15, 2018 by Alexey Kodanev Committed by David S. Miller Feb 16, 2018

udplite: fix partial checksum initialization



Since UDP-Lite is always using checksum, the following path is
triggered when calculating pseudo header for it:

  udp4_csum_init() or udp6_csum_init()
    skb_checksum_init_zero_check()
      __skb_checksum_validate_complete()

The problem can appear if skb->len is less than CHECKSUM_BREAK. In
this particular case __skb_checksum_validate_complete() also invokes
__skb_checksum_complete(skb). If UDP-Lite is using partial checksum
that covers only part of a packet, the function will return bad
checksum and the packet will be dropped.

It can be fixed if we skip skb_checksum_init_zero_check() and only
set the required pseudo header checksum for UDP-Lite with partial
checksum before udp4_csum_init()/udp6_csum_init() functions return.

Fixes: ed70fcfc ("net: Call skb_checksum_init in IPv4")
Fixes: e4f45b7f ("net: Call skb_checksum_init in IPv6")
Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent da279887

include/net/udplite.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -64,6 +64,7 @@ static inline int udplite_checksum_init(struct sk_buff skb, struct udphdr uh)
		UDP_SKB_CB(skb)->cscov = cscov;
		if (skb->ip_summed == CHECKSUM_COMPLETE)
		skb->ip_summed = CHECKSUM_NONE;
		skb->csum_valid = 0;
		}

		return 0;

net/ipv4/udp.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -2024,6 +2024,11 @@ static inline int udp4_csum_init(struct sk_buff skb, struct udphdr uh,
		err = udplite_checksum_init(skb, uh);
		if (err)
		return err;

		if (UDP_SKB_CB(skb)->partial_cov) {
		skb->csum = inet_compute_pseudo(skb, proto);
		return 0;
		}
		}

		/* Note, we are only interested in != 0 or == 0, thus the

net/ipv6/ip6_checksum.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -73,6 +73,11 @@ int udp6_csum_init(struct sk_buff skb, struct udphdr uh, int proto)
		err = udplite_checksum_init(skb, uh);
		if (err)
		return err;

		if (UDP_SKB_CB(skb)->partial_cov) {
		skb->csum = ip6_compute_pseudo(skb, proto);
		return 0;
		}
		}

		/* To support RFC 6936 (allow zero checksum in UDP/IPV6 for tunnels)

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