netdev - Re: [Intel-wired-lan] [PATCH] igc: fix a log entry using uninitialized netdev

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Message-ID: <ZioKlQR9z8RWGFAB@calimero.vinschen.de>
Date: Thu, 25 Apr 2024 09:47:33 +0200
From: Corinna Vinschen <vinschen@...hat.com>
To: Vinicius Costa Gomes <vinicius.gomes@...el.com>
Cc: Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
	intel-wired-lan@...ts.osuosl.org
Subject: Re: [Intel-wired-lan] [PATCH] igc: fix a log entry using
 uninitialized netdev

On Apr 24 17:06, Vinicius Costa Gomes wrote:
> Andrew Lunn <andrew@...n.ch> writes:
> 
> > On Tue, Apr 23, 2024 at 12:24:54PM +0200, Corinna Vinschen wrote:
> >> During successful probe, igc logs this:
> >> 
> >> [    5.133667] igc 0000:01:00.0 (unnamed net_device) (uninitialized): PHC added
> >>                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >> The reason is that igc_ptp_init() is called very early, even before
> >> register_netdev() has been called. So the netdev_info() call works
> >> on a partially uninitialized netdev.
> >> 
> >> Fix this by calling igc_ptp_init() after register_netdev(), right
> >> after the media autosense check, just as in igb.  Add a comment,
> >> just as in igb.
> >
> > The network stack can start sending and receiving packet before
> > register_netdev() returns. This is typical of NFS root for example. Is
> > there anything in igc_ptp_init() which could cause such packet
> > transfers to explode?
> >
> 
> There might be a very narrow window (probably impossible?), what I can
> see is:
> 
> 1. the netdevice is exposed to userspace;
> 2. userspace does the SIOCSHWTSTAMP ioctl() to enable TX timestamps;
> 3. userspace sends a packet that is going to be timestamped;
> 
> if this happens before igc_ptp_init() is called, adapter->ptp_tx_lock is
> going to be uninitialized, and (3) is going to crash.

The same would then be possible on igb as well, wouldn't it?


> If there's anything that makes this impossible/extremely unlikely, the
> patch looks good:
> 
> Acked-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> 
> 
> Cheers,
> -- 
> Vinicius


Corinna