From: Jiayuan Chen bond_rr_gen_slave_id() dereferences bond->rr_tx_counter without a NULL check. rr_tx_counter is a per-CPU counter only allocated in bond_open() when the bond mode is round-robin. If the bond device was never brought up, rr_tx_counter remains NULL, causing a null-ptr-deref. The XDP redirect path can reach this code even when the bond is not up: bpf_master_redirect_enabled_key is a global static key, so when any bond device has native XDP attached, the XDP_TX -> xdp_master_redirect() interception is enabled for all bond slaves system-wide. This allows the path xdp_master_redirect() -> bond_xdp_get_xmit_slave() -> bond_xdp_xmit_roundrobin_slave_get() -> bond_rr_gen_slave_id() to be reached on a bond that was never opened. The normal TX path (bond_xmit_roundrobin) is not affected because TX requires the bond to be UP, which guarantees rr_tx_counter is allocated. However, bond_xmit_get_slave() (ndo_get_xmit_slave) has the same code pattern via bond_xmit_roundrobin_slave_get() and could theoretically hit the same issue. Fix this by introducing bond_create_init() to allocate rr_tx_counter unconditionally at device creation time. It is called from both bond_create() and bond_newlink() before register_netdevice(), and returns -ENOMEM on failure so callers can propagate the error cleanly. bond_setup() is not suitable for this allocation as it is a void callback with no error return path. The conditional allocation in bond_open() is removed. Since bond_destructor() already unconditionally calls free_percpu(bond->rr_tx_counter), the lifecycle is clean: allocate at creation, free at destruction. Fixes: 879af96ffd72 ("net, core: Add support for XDP redirection to slave device") Reported-by: syzbot+80e046b8da2820b6ba73@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/698f84c6.a70a0220.2c38d7.00cc.GAE@google.com/T/ Signed-off-by: Jiayuan Chen --- drivers/net/bonding/bond_main.c | 18 ++++++++++++------ drivers/net/bonding/bond_netlink.c | 4 ++++ include/net/bonding.h | 1 + 3 files changed, 17 insertions(+), 6 deletions(-) diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index 78cff904cdc3..806034dc301f 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -4273,18 +4273,18 @@ void bond_work_cancel_all(struct bonding *bond) cancel_delayed_work_sync(&bond->peer_notify_work); } +int bond_create_init(struct bonding *bond) +{ + bond->rr_tx_counter = alloc_percpu(u32); + return bond->rr_tx_counter ? 0 : -ENOMEM; +} + static int bond_open(struct net_device *bond_dev) { struct bonding *bond = netdev_priv(bond_dev); struct list_head *iter; struct slave *slave; - if (BOND_MODE(bond) == BOND_MODE_ROUNDROBIN && !bond->rr_tx_counter) { - bond->rr_tx_counter = alloc_percpu(u32); - if (!bond->rr_tx_counter) - return -ENOMEM; - } - /* reset slave->backup and slave->inactive */ if (bond_has_slaves(bond)) { bond_for_each_slave(bond, slave, iter) { @@ -6458,6 +6458,12 @@ int bond_create(struct net *net, const char *name) dev_net_set(bond_dev, net); bond_dev->rtnl_link_ops = &bond_link_ops; + res = bond_create_init(bond); + if (res) { + free_netdev(bond_dev); + goto out; + } + res = register_netdevice(bond_dev); if (res < 0) { free_netdev(bond_dev); diff --git a/drivers/net/bonding/bond_netlink.c b/drivers/net/bonding/bond_netlink.c index 286f11c517f7..91595df85f06 100644 --- a/drivers/net/bonding/bond_netlink.c +++ b/drivers/net/bonding/bond_netlink.c @@ -598,6 +598,10 @@ static int bond_newlink(struct net_device *bond_dev, struct nlattr **tb = params->tb; int err; + err = bond_create_init(bond); + if (err) + return err; + err = register_netdevice(bond_dev); if (err) return err; diff --git a/include/net/bonding.h b/include/net/bonding.h index 4ad5521e7731..dac4725f3ac0 100644 --- a/include/net/bonding.h +++ b/include/net/bonding.h @@ -714,6 +714,7 @@ void bond_slave_arr_work_rearm(struct bonding *bond, unsigned long delay); void bond_peer_notify_work_rearm(struct bonding *bond, unsigned long delay); void bond_work_init_all(struct bonding *bond); void bond_work_cancel_all(struct bonding *bond); +int bond_create_init(struct bonding *bond); #ifdef CONFIG_PROC_FS void bond_create_proc_entry(struct bonding *bond); -- 2.43.0