From: Jiayuan Chen <[email protected]>
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.
Fix this by adding a NULL check with unlikely() in bond_rr_gen_slave_id()
before dereferencing rr_tx_counter. When rr_tx_counter is NULL (bond was
never opened), fall back to get_random_u32() for slave selection. The
allocation in bond_open() is kept, with WRITE_ONCE() added to safely
publish the pointer to the XDP read side. A plain read suffices for the
!bond->rr_tx_counter guard in bond_open() itself, as bond_open() runs
under RTNL lock and is the only writer of rr_tx_counter.
Fixes: 879af96ffd72 ("net, core: Add support for XDP redirection to slave
device")
Reported-by: [email protected]
Closes:
https://lore.kernel.org/all/[email protected]/T/
Signed-off-by: Jiayuan Chen <[email protected]>
---
drivers/net/bonding/bond_main.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 444519078da3..b8ec87625ce3 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -4290,9 +4290,11 @@ static int bond_open(struct net_device *bond_dev)
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)
+ u32 __percpu *rr_tx_tmp = alloc_percpu(u32);
+
+ if (!rr_tx_tmp)
return -ENOMEM;
+ WRITE_ONCE(bond->rr_tx_counter, rr_tx_tmp);
}
/* reset slave->backup and slave->inactive */
@@ -4883,6 +4885,9 @@ static u32 bond_rr_gen_slave_id(struct bonding *bond)
struct reciprocal_value reciprocal_packets_per_slave;
int packets_per_slave = bond->params.packets_per_slave;
+ if (unlikely(!READ_ONCE(bond->rr_tx_counter)))
+ return get_random_u32();
+
switch (packets_per_slave) {
case 0:
slave_id = get_random_u32();
--
2.43.0
