netdev - RE: [PATCH net] core: Don't attempt to load the "" driver.

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D17487151@AcuExch.aculab.com>
Date:	Thu, 4 Sep 2014 08:33:05 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Stephen Hemminger' <stephen@...workplumber.org>,
	Cong Wang <cwang@...pensource.com>
CC:	Linux Netdev List <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>
Subject: RE: [PATCH net] core: Don't attempt to load the "" driver.

From: Stephen Hemminger
> Cong Wang <cwang@...pensource.com> wrote:
> 
> > On Wed, Sep 3, 2014 at 2:02 AM, David Laight <David.Laight@...lab.com> wrote:
> > >> On Tue, Sep 2, 2014 at 6:48 AM, David Laight <David.Laight@...lab.com> wrote:
> > >> > While the applications shouldn't be calling an SIOCxxx ioctl with ifr_name[0] == 0
> > >> > the kernel shouldn't be tracing the error either.
> > >> >
> > >>
> > >> Why don't we reject this empty string? It doesn't look like a valid one.
> > >> I assume this is for compatibility?
> > >
> > > The ioctl code will error it later on - the module load is 'speculative'.
> > > Analysing whether all the ioctls need dev_load() to succeed is another issue.
> > >
> > > Indeed I'm not sure anything stops the module being unloaded before the
> > > ioctl action tries to take a real reference on the interface.
> > >
> > > Whether request_module("") should be an error is a different question,
> > > probably much harder to analyse.
> > >
> >
> > If an empty string is an invalid name, we definitely should reject it from
> > the very beginning, so that you would not need to worry about the above
> > issues.
> >
> > Something like the attached patch.
> 
> This will break for many things where the code randomly tries
> to load something based on name, but the module is already there.

Or the interface isn't generated buy a module etc.

Also ISTR seeing dev_load() being used as an initialiser for something.
So it isn't easy to change the prototype - otherwise I'd have suggested
tracing the failing ioctl cmd to make it easier to determine where the
invalid request was coming from.

	David



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