From: Sowmini Varadhan <sowmini.varadhan@oracle.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: Network Development <netdev@vger.kernel.org>,
David Miller <davem@davemloft.net>,
rds-devel@oss.oracle.com,
Santosh Shilimkar <santosh.shilimkar@oracle.com>
Subject: Re: [PATCH net-next] RDS: deliver zerocopy completion notification with data as an optimization
Date: Thu, 22 Feb 2018 08:36:05 -0500 [thread overview]
Message-ID: <20180222133605.GA32463@oracle.com> (raw)
In-Reply-To: <CAF=yD-+ZRyGmQ1z2ss-HWWy=LrZfmzjbG+KkRH1gbNSVVun-MA@mail.gmail.com>
On (02/21/18 19:39), Willem de Bruijn wrote:
> >> By the way, the put_cmsg is unconditional even if the caller did
> >> not supply msg_control. So it is basically no longer safe to ever
> >> call read, recv or recvfrom on a socket if zerocopy notifications
> >> are outstanding.
> >
> > Wait, I thought put_cmsg already checks for these things.
>
> It does, and sets MSG_CTRUNC to signal that it was unable to
> write all control data. But by then the notifications have already
> been dequeued.
Putting hyperbole about "no longer safe to ever call read etc" aside,
put_cmsg can also return EFAULT if uspace provides a bogus cmsghdr,
(i.e., copy_to_user fails). So the only thing you can do to really
protect against every possible thing is to requeue the notification
if put_cmsg fails.
prev parent reply other threads:[~2018-02-22 13:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-21 20:19 [PATCH net-next] RDS: deliver zerocopy completion notification with data as an optimization Sowmini Varadhan
2018-02-21 21:04 ` Santosh Shilimkar
2018-02-21 21:54 ` Willem de Bruijn
2018-02-21 22:14 ` Sowmini Varadhan
2018-02-21 22:50 ` Willem de Bruijn
2018-02-21 23:03 ` Sowmini Varadhan
2018-02-21 23:45 ` Willem de Bruijn
2018-02-22 0:26 ` Sowmini Varadhan
2018-02-22 0:39 ` Willem de Bruijn
2018-02-22 13:36 ` Sowmini Varadhan [this message]
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