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

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Message-ID:
 <BY3PR18MB4721ADC9261427273EE8ACF6C73B2@BY3PR18MB4721.namprd18.prod.outlook.com>
Date: Mon, 16 Dec 2024 18:24:58 +0000
From: Shinas Rasheed <srasheed@...vell.com>
To: Larysa Zaremba <larysa.zaremba@...el.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Haseeb Gani
	<hgani@...vell.com>, Sathesh B Edara <sedara@...vell.com>,
        Vimlesh Kumar
	<vimleshk@...vell.com>,
        "thaller@...hat.com" <thaller@...hat.com>,
        "wizhao@...hat.com" <wizhao@...hat.com>,
        "kheib@...hat.com"
	<kheib@...hat.com>,
        "konguyen@...hat.com" <konguyen@...hat.com>,
        "horms@...nel.org" <horms@...nel.org>,
        "einstein.xue@...axg.com"
	<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: [EXTERNAL] Re: [PATCH net v2 1/4] octeon_ep: fix race conditions
 in ndo_get_stats64

Hi Larysa,

> 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://urldefense.proofpoint.com/v2/url?u=https-
> 3A__lore.kernel.org_all_20241203072130.2316913-2D2-2Dsrasheed-
> 40marvell.com_&d=DwIBAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=1OxLD4y-
> oxrlgQ1rjXgWtmLz1pnaDjD96sDq-
> cKUwK4&m=SfdHxslanlPmhVsD4m3qSuUI2eout0Tqi9o-
> DnPbfjVzv5Nte11HnOw2-aIeEN3i&s=0iv3vwi5W-
> le8dxI6EtazU7q4RlnvElcVk5MsyMm_0k&e=
> >
> >  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?

The octep_get_stats64() is an instance of the ndo_get_stats64() netdev op. As I understand, the netdev op is supposed to be
called from RCU-safe contexts. Please do correct me if I'm wrong.