linux-kernel - RE: [PATCH 32/33] sctp: add sctp_sock_get_primary

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Date:   Thu, 14 May 2020 09:51:00 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Marcelo Ricardo Leitner' <marcelo.leitner@...il.com>,
        Christoph Hellwig <hch@....de>
CC:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Vlad Yasevich <vyasevich@...il.com>,
        Neil Horman <nhorman@...driver.com>,
        Jon Maloy <jmaloy@...hat.com>,
        Ying Xue <ying.xue@...driver.com>,
        "drbd-dev@...ts.linbit.com" <drbd-dev@...ts.linbit.com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "target-devel@...r.kernel.org" <target-devel@...r.kernel.org>,
        "linux-afs@...ts.infradead.org" <linux-afs@...ts.infradead.org>,
        "linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>,
        "cluster-devel@...hat.com" <cluster-devel@...hat.com>,
        "ocfs2-devel@....oracle.com" <ocfs2-devel@....oracle.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
        "ceph-devel@...r.kernel.org" <ceph-devel@...r.kernel.org>,
        "rds-devel@....oracle.com" <rds-devel@....oracle.com>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>
Subject: RE: [PATCH 32/33] sctp: add sctp_sock_get_primary_addr

From: Marcelo Ricardo Leitner
> Sent: 13 May 2020 19:03
> 
> On Wed, May 13, 2020 at 08:26:47AM +0200, Christoph Hellwig wrote:
> > Add a helper to directly get the SCTP_PRIMARY_ADDR sockopt from kernel
> > space without going through a fake uaccess.
> 
> Same comment as on the other dlm/sctp patch.

Wouldn't it be best to write sctp_[gs]etsockotp() that
use a kernel buffer and then implement the user-space
calls using a wrapper that does the copies to an on-stack
(or malloced if big) buffer.

That will also simplify the code be removing all the copies
and -EFAULT returns.
Only the size checks will be needed and the code can assume
the buffer is at least the size of the on-stack buffer.

Our SCTP code uses SO_REUSADDR, SCTP_EVENTS, SCTP_NODELAY,
SCTP_STATUS, SCTP_INITMSG, IPV6_ONLY, SCTP_SOCKOPT_BINDX_ADD
and SO_LINGER.

	David

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