[Eulerkernel] [PATCH] af_unix: dont send SCM_CREDENTIAL when dest socket is NULL

[dingtianhong <dingtianhong@huawei.com>]

SCM_SCREDENTIALS should apply to write() syscalls only either source or destination
socket asserted SOCK_PASSCRED. The original implememtation in maybe_add_creds is wrong,
and breaks several LSB testcases ( i.e. /tset/LSB.os/netowkr/recvfrom/T.recvfrom).

Origionally-authored-by: Karel Srot <ksrot@redhat.com>
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
---
   net/unix/af_unix.c | 4 ++--
   1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 51be64f..99189fd 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1413,8 +1413,8 @@ static void maybe_add_creds(struct sk_buff *skb, const struct socket *sock,
          if (UNIXCB(skb).cred)
                  return;
          if (test_bit(SOCK_PASSCRED, &sock->flags) ||
-           !other->sk_socket ||
-           test_bit(SOCK_PASSCRED, &other->sk_socket->flags)) {
+           (other->sk_socket &&
+           test_bit(SOCK_PASSCRED, &other->sk_socket->flags))) {
                  UNIXCB(skb).pid  = get_pid(task_tgid(current));
                  UNIXCB(skb).cred = get_current_cred();
          }
--