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

[Eric Dumazet <eric.dumazet@gmail.com>]

On Mon, 2013-03-25 at 18:28 +0800, dingtianhong wrote:
> 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();
>           }

I am not sure why adding credentials if other->sk_socket is NULL could
break an application ?

This was the case before commit introducing this code.

Anyway patch looks fine

Acked-by: Eric Dumazet <edumazet@google.com>