netdev - Re: [PATCH] netlink: Fix netlink_recvmsg() handling of error from netlink

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Message-ID: <20140709173254.GD4291@nicira.com>
Date:	Wed, 9 Jul 2014 10:32:54 -0700
From:	Ben Pfaff <blp@...ira.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] netlink: Fix netlink_recvmsg() handling of error from
 netlink_dump().

On Mon, Jul 07, 2014 at 07:37:35PM -0700, David Miller wrote:
> From: Ben Pfaff <blp@...ira.com>
> Date: Mon, 30 Jun 2014 15:35:04 -0700
> 
> > netlink_dump() returns a negative errno value on error.  Until now,
> > netlink_recvmsg() directly recorded that negative value in sk->sk_err,
> > but that's wrong since sk_err takes positive errno values.  (This manifests
> > as userspace receiving a positive return value from the recv() system call,
> > falsely indicating success.)
> > 
> > This bug was introduced in the commit that started checking the
> > netlink_dump() return value, commit b44d211 (netlink: handle errors from
> > netlink_dump()).
> > 
> > Multithreaded Netlink dumps are one way to trigger this behavior in
> > practice, as described in the commit message for the userspace workaround
> > posted here:
> >     http://openvswitch.org/pipermail/dev/2014-June/042339.html
> > 
> > Signed-off-by: Ben Pfaff <blp@...ira.com>
> 
> There's another place, later in this file, doing the same exact thing.
> 
> Please respin this patch, fixing that location too.

Thanks for pointing that out, I sent out v2.
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