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

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Message-ID: <29ef00f0-57dc-4332-9569-e88868a85575@redhat.com>
Date: Tue, 24 Sep 2024 12:20:41 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Jiwon Kim <jiwonaid0@...il.com>, razor@...ckwall.org, jv@...sburgh.net,
 andy@...yhouse.net, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, 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 9/18/24 16:06, 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>

Isn't the above issue completely addressed by explicitly checking for 
bond->prog in bond_xdp_get_xmit_slave()? Or would that broke some use-case?

Thanks,

Paolo