linux-kernel - Re: [PATCH net v3] bonding: Fix unnecessary warnings and logs from bond_xdp_get_xmit

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Message-ID: <8dfc3125-b4fd-4209-89c5-a5a85a1d65a6@blackwall.org>
Date: Fri, 20 Sep 2024 09:43:37 +0300
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Jiwon Kim <jiwonaid0@...il.com>, 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
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 bpf@...r.kernel.org, syzbot+c187823a52ed505b2257@...kaller.appspotmail.com
Subject: Re: [PATCH net v3] bonding: Fix unnecessary warnings and logs from
 bond_xdp_get_xmit_slave()

On 18/09/2024 17:06, Jiwon Kim wrote:
> syzbot reported a WARNING in bond_xdp_get_xmit_slave. To reproduce
> this[1], one bond device (bond1) has xdpdrv, which increases
> bpf_master_redirect_enabled_key. Another bond device (bond0) which is
> unsupported by XDP but its slave (veth3) has xdpgeneric that returns
> XDP_TX. This triggers WARN_ON_ONCE() from the xdp_master_redirect().
> To reduce unnecessary warnings and improve log management, we need to
> delete the WARN_ON_ONCE() and add ratelimit to the netdev_err().
> 
> [1] Steps to reproduce:
>     # Needs tx_xdp 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
>     # Increases bpf_master_redirect_enabled_key
>     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
>     # Triggers WARN_ON_ONCE() from the xdp_master_redirect()
>     ip l set veth3 xdpgeneric object tx_xdp.o section xdp_tx
> 
> 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>
> ---
> v3: Fix subject and description
> v2: Change the patch to fix bond_xdp_get_xmit_slave
> ---
>  drivers/net/bonding/bond_main.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index b560644ee1b1..b1bffd8e9a95 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -5610,9 +5610,9 @@ 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);
> +		if (net_ratelimit())
> +			netdev_err(bond_dev, "Unknown bonding mode %d for xdp xmit\n",
> +				   BOND_MODE(bond));
>  		return NULL;
>  	}
>  

Looks good to me, but next time wait 1 day before reposting another version.
Signed-off-by: Nikolay Aleksandrov <razor@...ckwall.org>