[PATCH 4.8 26/35] udp: fix IP_CHECKSUM handling

From: Greg Kroah-Hartman
Date: Sun Nov 13 2016 - 06:33:54 EST


4.8-stable review patch. If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@xxxxxxxxxx>


[ Upstream commit 10df8e6152c6c400a563a673e9956320bfce1871 ]

First bug was added in commit ad6f939ab193 ("ip: Add offset parameter to
ip_cmsg_recv") : Tom missed that ipv4 udp messages could be received on
AF_INET6 socket. ip_cmsg_recv(msg, skb) should have been replaced by
ip_cmsg_recv_offset(msg, skb, sizeof(struct udphdr));

Then commit e6afc8ace6dd ("udp: remove headers from UDP packets before
queueing") forgot to adjust the offsets now UDP headers are pulled
before skb are put in receive queue.

Fixes: ad6f939ab193 ("ip: Add offset parameter to ip_cmsg_recv")
Fixes: e6afc8ace6dd ("udp: remove headers from UDP packets before queueing")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Sam Kumar <samanthakumar@xxxxxxxxxx>
Cc: Willem de Bruijn <willemb@xxxxxxxxxx>
Tested-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/net/ip.h | 4 ++--
net/ipv4/ip_sockglue.c | 11 ++++++-----
net/ipv4/udp.c | 2 +-
net/ipv6/udp.c | 3 ++-
4 files changed, 11 insertions(+), 9 deletions(-)

--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -549,7 +549,7 @@ int ip_options_rcv_srr(struct sk_buff *s
*/

void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb);
-void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb, int offset);
+void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb, int tlen, int offset);
int ip_cmsg_send(struct sock *sk, struct msghdr *msg,
struct ipcm_cookie *ipc, bool allow_ipv6);
int ip_setsockopt(struct sock *sk, int level, int optname, char __user *optval,
@@ -571,7 +571,7 @@ void ip_local_error(struct sock *sk, int

static inline void ip_cmsg_recv(struct msghdr *msg, struct sk_buff *skb)
{
- ip_cmsg_recv_offset(msg, skb, 0);
+ ip_cmsg_recv_offset(msg, skb, 0, 0);
}

bool icmp_global_allow(void);
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -98,7 +98,7 @@ static void ip_cmsg_recv_retopts(struct
}

static void ip_cmsg_recv_checksum(struct msghdr *msg, struct sk_buff *skb,
- int offset)
+ int tlen, int offset)
{
__wsum csum = skb->csum;

@@ -106,8 +106,9 @@ static void ip_cmsg_recv_checksum(struct
return;

if (offset != 0)
- csum = csum_sub(csum, csum_partial(skb_transport_header(skb),
- offset, 0));
+ csum = csum_sub(csum,
+ csum_partial(skb_transport_header(skb) + tlen,
+ offset, 0));

put_cmsg(msg, SOL_IP, IP_CHECKSUM, sizeof(__wsum), &csum);
}
@@ -153,7 +154,7 @@ static void ip_cmsg_recv_dstaddr(struct
}

void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb,
- int offset)
+ int tlen, int offset)
{
struct inet_sock *inet = inet_sk(skb->sk);
unsigned int flags = inet->cmsg_flags;
@@ -216,7 +217,7 @@ void ip_cmsg_recv_offset(struct msghdr *
}

if (flags & IP_CMSG_CHECKSUM)
- ip_cmsg_recv_checksum(msg, skb, offset);
+ ip_cmsg_recv_checksum(msg, skb, tlen, offset);
}
EXPORT_SYMBOL(ip_cmsg_recv_offset);

--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1327,7 +1327,7 @@ try_again:
*addr_len = sizeof(*sin);
}
if (inet->cmsg_flags)
- ip_cmsg_recv_offset(msg, skb, sizeof(struct udphdr) + off);
+ ip_cmsg_recv_offset(msg, skb, sizeof(struct udphdr), off);

err = copied;
if (flags & MSG_TRUNC)
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -427,7 +427,8 @@ try_again:

if (is_udp4) {
if (inet->cmsg_flags)
- ip_cmsg_recv(msg, skb);
+ ip_cmsg_recv_offset(msg, skb,
+ sizeof(struct udphdr), off);
} else {
if (np->rxopt.all)
ip6_datagram_recv_specific_ctl(sk, msg, skb);