scm: fix a typo in put_cmsg()

We need to store cmlen instead of len in cm->cmsg_len.

Fixes: 38ebcf5096 ("scm: optimize put_cmsg()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/scm.c

@@ -232,7 +232,7 @@ int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
 		if (!user_write_access_begin(cm, cmlen))
 			goto efault;
 
-		unsafe_put_user(len, &cm->cmsg_len, efault_end);
+		unsafe_put_user(cmlen, &cm->cmsg_len, efault_end);
 		unsafe_put_user(level, &cm->cmsg_level, efault_end);
 		unsafe_put_user(type, &cm->cmsg_type, efault_end);
 		unsafe_copy_to_user(CMSG_USER_DATA(cm), data,