net: fix skb_add_data_nocache() to calc csum correctly

commit c6e1a0d12ca7b4f22c58e55a16beacfb7d3d8462 broken the calc
 (net: Allow no-cache copy from user on transmit)
of checksum, which may cause some tcp packets be dropped because
incorrect checksum. ssh does not work under today's net-next-2.6
tree.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Acked-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 7 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 43bd515e92fd..9cbf23c815f5 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1392,14 +1392,14 @@ static inline void sk_nocaps_add(struct sock *sk, int flags)
 
 static inline int skb_do_copy_data_nocache(struct sock *sk, struct sk_buff *skb,
                                            char __user *from, char *to,
-                                           int copy)
+                                           int copy, int offset)
 {
         if (skb->ip_summed == CHECKSUM_NONE) {
                 int err = 0;
                 __wsum csum = csum_and_copy_from_user(from, to, copy, 0, &err);
                 if (err)
                         return err;
-                skb->csum = csum_block_add(skb->csum, csum, skb->len);
+                skb->csum = csum_block_add(skb->csum, csum, offset);
         } else if (sk->sk_route_caps & NETIF_F_NOCACHE_COPY) {
                 if (!access_ok(VERIFY_READ, from, copy) ||
                     __copy_from_user_nocache(to, from, copy))
@@ -1413,11 +1413,12 @@ static inline int skb_do_copy_data_nocache(struct sock *sk, struct sk_buff *skb,
 static inline int skb_add_data_nocache(struct sock *sk, struct sk_buff *skb,
                                        char __user *from, int copy)
 {
-        int err;
+        int err, offset = skb->len;
 
-        err = skb_do_copy_data_nocache(sk, skb, from, skb_put(skb, copy), copy);
+        err = skb_do_copy_data_nocache(sk, skb, from, skb_put(skb, copy),
+                                       copy, offset);
         if (err)
-                __skb_trim(skb, skb->len);
+                __skb_trim(skb, offset);
 
         return err;
 }
@@ -1429,8 +1430,8 @@ static inline int skb_copy_to_page_nocache(struct sock *sk, char __user *from,
 {
         int err;
 
-        err = skb_do_copy_data_nocache(sk, skb, from,
-                                       page_address(page) + off, copy);
+        err = skb_do_copy_data_nocache(sk, skb, from, page_address(page) + off,
+                                       copy, skb->len);
         if (err)
                 return err;