linux-kernel - Re: [PATCH net v2] bonding: Add net_ratelimit for bond_xdp_get_xmit_slave in bond

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Message-ID: <CAKaoOqdCh41iBbzuZjx3mJpOXBh0aaLmBRd7Pz9jjwBFLqAifg@mail.gmail.com>
Date: Wed, 18 Sep 2024 23:07:24 +0900
From: Jiwon Kim <jiwonaid0@...il.com>
To: Nikolay Aleksandrov <razor@...ckwall.org>
Cc: jv@...sburgh.net, andy@...yhouse.net, davem@...emloft.net, 
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, ast@...nel.org, 
	daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com, 
	joamaki@...il.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	bpf@...r.kernel.org, syzbot+c187823a52ed505b2257@...kaller.appspotmail.com
Subject: Re: [PATCH net v2] bonding: Add net_ratelimit for bond_xdp_get_xmit_slave
 in bond_main.c

On Wed, Sep 18, 2024 at 6:51 PM Nikolay Aleksandrov <razor@...ckwall.org> wrote:
>
> On 18/09/2024 11:35, Jiwon Kim wrote:
> > Add net_ratelimit to reduce warnings and logs.
> > This addresses the WARNING in bond_xdp_get_xmit_slave reported by syzbot.
> >
>
> This commit message is severely lacking. I did the heavy lifting and gave you
> detailed analysis of the problem, please describe the actual issue and why
> this is ok to do. Also the subject is confusing, it should give a concise
> summary of what the patch is trying to do and please don't include filenames in it.
> You can take a look at other commits for examples.
>
> > Setup:
> >     # Need xdp_tx_prog with return XDP_TX;
> >     ip l add veth0 type veth peer veth1
> >     ip l add veth3 type veth peer veth4
> >     ip l add bond0 type bond mode 6 # <- BOND_MODE_ALB, unsupported by xdp
> >     ip l add bond1 type bond # <- BOND_MODE_ROUNDROBIN by default
> >     ip l set veth0 master bond1
> >     ip l set bond1 up
> >     ip l set dev bond1 xdpdrv object tx_xdp.o section xdp_tx
> >     ip l set veth3 master bond0
> >     ip l set bond0 up
> >     ip l set veth4 up
> >     ip l set veth3 xdpgeneric object tx_xdp.o section xdp_tx
>
> Care to explain why this setup would trigger anything?
>
> >
> > Reported-by: syzbot+c187823a52ed505b2257@...kaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=c187823a52ed505b2257
> > Fixes: 9e2ee5c7e7c3 ("net, bonding: Add XDP support to the bonding driver")
> > Signed-off-by: Jiwon Kim <jiwonaid0@...il.com>
> > ---
> > v2: Change the patch to fix bond_xdp_get_xmit_slave
> > ---
> >  drivers/net/bonding/bond_main.c | 9 ++++++---
> >  1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> > index b560644ee1b1..91b9cbdcf274 100644
> > --- a/drivers/net/bonding/bond_main.c
> > +++ b/drivers/net/bonding/bond_main.c
> > @@ -5610,9 +5610,12 @@ bond_xdp_get_xmit_slave(struct net_device *bond_dev, struct xdp_buff *xdp)
> >               break;
> >
> >       default:
> > -             /* Should never happen. Mode guarded by bond_xdp_check() */
> > -             netdev_err(bond_dev, "Unknown bonding mode %d for xdp xmit\n", BOND_MODE(bond));
> > -             WARN_ON_ONCE(1);
> > +             /* This might occur when a bond device increases bpf_master_redirect_enabled_key,
> > +              * and another bond device with XDP_TX and bond slave.
> > +              */
>
> The comment is confusing and needs to be reworded or dropped altogether.
>
> > +             if (net_ratelimit())
> > +                     netdev_err(bond_dev, "Unknown bonding mode %d for xdp xmit\n",
> > +                                BOND_MODE(bond));
> >               return NULL;
> >       }
> >
>

Hi Nikolay,

I have taken the time to review your feedback and have sent [PATCH net
v3] for your consideration.
Please take a look when you have a moment.

Thank you so much!

Sincerely,

Jiwon Kim