Re: [PATCH v1 net-next 06/12] af_unix: Reuse out_pipe label in unix_stream_sendmsg().

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: Simon Horman <horms@kernel.org>
Date: Fri, 10 Jan 2025 11:43:44 +0000
> On Fri, Jan 10, 2025 at 06:26:35PM +0900, Kuniyuki Iwashima wrote:
> > This is a follow-up of commit d460b04bc452 ("af_unix: Clean up
> > error paths in unix_stream_sendmsg().").
> > 
> > If we initialise skb with NULL in unix_stream_sendmsg(), we can
> > reuse the existing out_pipe label for the SEND_SHUTDOWN check.
> > 
> > Let's rename do it and adjust the existing label as out_pipe_lock.
> > 
> > While at it, size and data_len are moved to the while loop scope.
> > 
> > Suggested-by: Paolo Abeni <pabeni@redhat.com>
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> > ---
> >  net/unix/af_unix.c | 23 +++++++++--------------
> >  1 file changed, 9 insertions(+), 14 deletions(-)
> > 
> > diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> > index b190ea8b8e9d..6505eeab9957 100644
> > --- a/net/unix/af_unix.c
> > +++ b/net/unix/af_unix.c
> 
> ...
> 
> > @@ -2285,16 +2283,12 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
> >  		}
> >  	}
> >  
> > -	if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN) {
> > -		if (!(msg->msg_flags & MSG_NOSIGNAL))
> > -			send_sig(SIGPIPE, current, 0);
> > -
> > -		err = -EPIPE;
> > -		goto out_err;
> > -	}
> > +	if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
> 
> Hi Iwashima-san,
> 
> I think you need to set reason here.
> 
> Flagged by W=1 builds with clang-19.

Hi Simon,

I didn't set it here because skb == NULL and kfree_skb()
doesn't touch reason, and KMSAN won't complain about uninit.

Should I use SKB_NOT_DROPPED_YET or drop patch 6 or leave
it as is ?

What do you think ?

Thanks!