On 9/24/24 13:20, Paolo Abeni wrote: > 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@xxxxxxxxxxxxxxxxxxxxxxxxx >> 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@xxxxxxxxx> > > 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 > There isn't much difference with this patch, bond_xdp_get_xmit_slave() always returns either a slave or NULL, either way you'd return NULL. It does have a potential to break some weird setup, but I can't currently come up with one where bond_xdp_get_xmit_slave is used and xdp_prog is not set, so I don't have a preference about which way to fix it. :) Cheers, Nik
