Subject: Re: [PATCH net 1/2] sctp: remove redundant assignment when call sctp_get_port_local

From: Marcelo Ricardo Leitner <[email-masked]>
Date: Wed, 11 Sep 2019 11:30:08 -0300

On Wed, Sep 11, 2019 at 11:30:38AM +0300, Dan Carpenter wrote:
> On Wed, Sep 11, 2019 at 09:30:47AM +0800, maowenan wrote:
> > 
> > 
> > On 2019/9/11 3:22, Dan Carpenter wrote:
> > > On Tue, Sep 10, 2019 at 09:57:10PM +0300, Dan Carpenter wrote:
> > >> On Tue, Sep 10, 2019 at 03:13:42PM +0800, Mao Wenan wrote:
> > >>> There are more parentheses in if clause when call sctp_get_port_local
> > >>> in sctp_do_bind, and redundant assignment to 'ret'. This patch is to
> > >>> do cleanup.
> > >>>
> > >>> Signed-off-by: Mao Wenan <[email-masked]>
> > >>> ---
> > >>>  net/sctp/socket.c | 3 +--
> > >>>  1 file changed, 1 insertion(+), 2 deletions(-)
> > >>>
> > >>> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> > >>> index 9d1f83b10c0a..766b68b55ebe 100644
> > >>> --- a/net/sctp/socket.c
> > >>> +++ b/net/sctp/socket.c
> > >>> @@ -399,9 +399,8 @@ static int sctp_do_bind(struct sock *sk, union sctp_addr *addr, int len)
> > >>>  	 * detection.
> > >>>  	 */
> > >>>  	addr->v4.sin_port = htons(snum);
> > >>> -	if ((ret = sctp_get_port_local(sk, addr))) {
> > >>> +	if (sctp_get_port_local(sk, addr))
> > >>>  		return -EADDRINUSE;
> > >>
> > >> sctp_get_port_local() returns a long which is either 0,1 or a pointer
> > >> casted to long.  It's not documented what it means and neither of the
> > >> callers use the return since commit 62208f12451f ("net: sctp: simplify
> > >> sctp_get_port").
> > > 
> > > Actually it was commit 4e54064e0a13 ("sctp: Allow only 1 listening
> > > socket with SO_REUSEADDR") from 11 years ago.  That patch fixed a bug,
> > > because before the code assumed that a pointer casted to an int was the
> > > same as a pointer casted to a long.
> > 
> > commit 4e54064e0a13 treated non-zero return value as unexpected, so the current
> > cleanup is ok?
> 
> Yeah.  It's fine, I was just confused why we weren't preserving the
> error code and then I saw that we didn't return errors at all and got
> confused.

But please lets seize the moment and do the change Dean suggested.
This was the last place saving this return value somewhere. It makes
sense to cleanup sctp_get_port_local() now and remove that masked
pointer return.

Then you may also cleanup:
socket.c:       return !!sctp_get_port_local(sk, &addr);
as it will be a direct map.

  Marcelo