linux-kernel - Re: [PATCH net v2 1/4] octeon_ep: fix race conditions in ndo_get

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Message-ID: <Z2A9UmjW7rnCGiEu@lzaremba-mobl.ger.corp.intel.com>
Date: Mon, 16 Dec 2024 15:46:42 +0100
From: Larysa Zaremba <larysa.zaremba@...el.com>
To: Shinas Rasheed <srasheed@...vell.com>
CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<hgani@...vell.com>, <sedara@...vell.com>, <vimleshk@...vell.com>,
	<thaller@...hat.com>, <wizhao@...hat.com>, <kheib@...hat.com>,
	<konguyen@...hat.com>, <horms@...nel.org>, <einstein.xue@...axg.com>,
	Veerasenareddy Burru <vburru@...vell.com>, Andrew Lunn
	<andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, "Eric
 Dumazet" <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, Abhijit Ayarekar <aayarekar@...vell.com>, "Satananda
 Burla" <sburla@...vell.com>
Subject: Re: [PATCH net v2 1/4] octeon_ep: fix race conditions in
 ndo_get_stats64

On Mon, Dec 16, 2024 at 03:30:12PM +0100, Larysa Zaremba wrote:
> On Sun, Dec 15, 2024 at 11:58:39PM -0800, Shinas Rasheed wrote:
> > ndo_get_stats64() can race with ndo_stop(), which frees input and
> > output queue resources. Call synchronize_net() to avoid such races.
> > 
> > Fixes: 6a610a46bad1 ("octeon_ep: add support for ndo ops")
> > Signed-off-by: Shinas Rasheed <srasheed@...vell.com>
> > ---
> > V2:
> >   - Changed sync mechanism to fix race conditions from using an atomic
> >     set_bit ops to a much simpler synchronize_net()
> > 
> > V1: https://lore.kernel.org/all/20241203072130.2316913-2-srasheed@marvell.com/
> > 
> >  drivers/net/ethernet/marvell/octeon_ep/octep_main.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/net/ethernet/marvell/octeon_ep/octep_main.c b/drivers/net/ethernet/marvell/octeon_ep/octep_main.c
> > index 549436efc204..941bbaaa67b5 100644
> > --- a/drivers/net/ethernet/marvell/octeon_ep/octep_main.c
> > +++ b/drivers/net/ethernet/marvell/octeon_ep/octep_main.c
> > @@ -757,6 +757,7 @@ static int octep_stop(struct net_device *netdev)
> >  {
> >  	struct octep_device *oct = netdev_priv(netdev);
> >  
> > +	synchronize_net();
> 
> You should have elaborated on the fact that this synchronize_net() is for 
> __LINK_STATE_START flag in the commit message, this is not obvious. Also, is 
> octep_get_stats64() called from RCU-safe context?
>

Now I see that in case !netif_running(), you do not bail out of 
octep_get_stats64() fully (or at all after the second patch). So, could you 
explain, how are you utilizing RCU here?

> >  	netdev_info(netdev, "Stopping the device ...\n");
> >  
> >  	octep_ctrl_net_set_link_status(oct, OCTEP_CTRL_NET_INVALID_VFID, false,
> > -- 
> > 2.25.1
> > 
> > 
>