[PATCH 6.18 010/122] bonding: annotate data-races around slave->last_rx

Greg Kroah-Hartman
2026-02-04T15:28:28Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit f6c3665b6dc53c3ab7d31b585446a953a74340ef ]

slave->last_rx and slave->target_last_arp_rx[...] can be read and written
locklessly. Add READ_ONCE() and WRITE_ONCE() annotations.

syzbot reported:

BUG: KCSAN: data-race in bond_rcv_validate / bond_rcv_validate

write to 0xffff888149f0d428 of 8 bytes by interrupt on cpu 1:
bond_rcv_validate+0x202/0x7a0 drivers/net/bonding/bond_main.c:3335
bond_handle_frame+0xde/0x5e0 drivers/net/bonding/bond_main.c:1533
__netif_receive_skb_core+0x5b1/0x1950 net/core/dev.c:6039
__netif_receive_skb_one_core net/core/dev.c:6150 [inline]
__netif_receive_skb+0x59/0x270 net/core/dev.c:6265
netif_receive_skb_internal net/core/dev.c:6351 [inline]
netif_receive_skb+0x4b/0x2d0 net/core/dev.c:6410
...

write to 0xffff888149f0d428 of 8 bytes by interrupt on cpu 0:
bond_rcv_validate+0x202/0x7a0 drivers/net/bonding/bond_main.c:3335
bond_handle_frame+0xde/0x5e0 drivers/net/bonding/bond_main.c:1533
__netif_receive_skb_core+0x5b1/0x1950 net/core/dev.c:6039
__netif_receive_skb_one_core net/core/dev.c:6150 [inline]
__netif_receive_skb+0x59/0x270 net/core/dev.c:6265
netif_receive_skb_internal net/core/dev.c:6351 [inline]
netif_receive_skb+0x4b/0x2d0 net/core/dev.c:6410
br_netif_receive_skb net/bridge/br_input.c:30 [inline]
NF_HOOK include/linux/netfilter.h:318 [inline]
...

value changed: 0x0000000100005365 -> 0x0000000100005366

Fixes: f5b2b966f032 ("[PATCH] bonding: Validate probe replies in ARP monitor")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Link: https://patch.msgid.link/20260122162914.2299312-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/bonding/bond_main.c | 18 ++++++++++--------
drivers/net/bonding/bond_options.c | 8 ++++----
include/net/bonding.h | 13 +++++++------
3 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 595fda2444b1f..99adfffcca044 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3138,8 +3138,8 @@ static void bond_validate_arp(struct bonding *bond, struct slave *slave, __be32
__func__, &sip);
return;
}
- slave->last_rx = jiffies;
- slave->target_last_arp_rx[i] = jiffies;
+ WRITE_ONCE(slave->last_rx, jiffies);
+ WRITE_ONCE(slave->target_last_arp_rx[i], jiffies);
}

static int bond_arp_rcv(const struct sk_buff *skb, struct bonding *bond,
@@ -3358,8 +3358,8 @@ static void bond_validate_na(struct bonding *bond, struct slave *slave,
__func__, saddr);
return;
}
- slave->last_rx = jiffies;
- slave->target_last_arp_rx[i] = jiffies;
+ WRITE_ONCE(slave->last_rx, jiffies);
+ WRITE_ONCE(slave->target_last_arp_rx[i], jiffies);
}

static int bond_na_rcv(const struct sk_buff *skb, struct bonding *bond,
@@ -3429,7 +3429,7 @@ int bond_rcv_validate(const struct sk_buff *skb, struct bonding *bond,
(slave_do_arp_validate_only(bond) && is_ipv6) ||
#endif
!slave_do_arp_validate_only(bond))
- slave->last_rx = jiffies;
+ WRITE_ONCE(slave->last_rx, jiffies);
return RX_HANDLER_ANOTHER;
} else if (is_arp) {
return bond_arp_rcv(skb, bond, slave);
@@ -3497,7 +3497,7 @@ static void bond_loadbalance_arp_mon(struct bonding *bond)

if (slave->link != BOND_LINK_UP) {
if (bond_time_in_interval(bond, last_tx, 1) &&
- bond_time_in_interval(bond, slave->last_rx, 1)) {
+ bond_time_in_interval(bond, READ_ONCE(slave->last_rx), 1)) {

bond_propose_link_state(slave, BOND_LINK_UP);
slave_state_changed = 1;
@@ -3521,8 +3521,10 @@ static void bond_loadbalance_arp_mon(struct bonding *bond)
* when the source ip is 0, so don't take the link down
* if we don't know our ip yet
*/
- if (!bond_time_in_interval(bond, last_tx, bond->params.missed_max) ||
- !bond_time_in_interval(bond, slave->last_rx, bond->params.missed_max)) {
+ if (!bond_time_in_interval(bond, last_tx,
+ bond->params.missed_max) ||
+ !bond_time_in_interval(bond, READ_ONCE(slave->last_rx),
+ bond->params.missed_max)) {

bond_propose_link_state(slave, BOND_LINK_DOWN);
slave_state_changed = 1;
diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
index 384499c869b8d..f1c6e9d8f6167 100644
--- a/drivers/net/bonding/bond_options.c
+++ b/drivers/net/bonding/bond_options.c
@@ -1152,7 +1152,7 @@ static void _bond_options_arp_ip_target_set(struct bonding *bond, int slot,

if (slot >= 0 && slot < BOND_MAX_ARP_TARGETS) {
bond_for_each_slave(bond, slave, iter)
- slave->target_last_arp_rx[slot] = last_rx;
+ WRITE_ONCE(slave->target_last_arp_rx[slot], last_rx);
targets[slot] = target;
}
}
@@ -1221,8 +1221,8 @@ static int bond_option_arp_ip_target_rem(struct bonding *bond, __be32 target)
bond_for_each_slave(bond, slave, iter) {
targets_rx = slave->target_last_arp_rx;
for (i = ind; (i < BOND_MAX_ARP_TARGETS-1) && targets[i+1]; i++)
- targets_rx[i] = targets_rx[i+1];
- targets_rx[i] = 0;
+ WRITE_ONCE(targets_rx[i], READ_ONCE(targets_rx[i+1]));
+ WRITE_ONCE(targets_rx[i], 0);
}
for (i = ind; (i < BOND_MAX_ARP_TARGETS-1) && targets[i+1]; i++)
targets[i] = targets[i+1];
@@ -1377,7 +1377,7 @@ static void _bond_options_ns_ip6_target_set(struct bonding *bond, int slot,

if (slot >= 0 && slot < BOND_MAX_NS_TARGETS) {
bond_for_each_slave(bond, slave, iter) {
- slave->target_last_arp_rx[slot] = last_rx;
+ WRITE_ONCE(slave->target_last_arp_rx[slot], last_rx);
slave_set_ns_maddr(bond, slave, target, &targets[slot]);
}
targets[slot] = *target;
diff --git a/include/net/bonding.h b/include/net/bonding.h
index 49edc7da05867..4620784035570 100644
--- a/include/net/bonding.h
+++ b/include/net/bonding.h
@@ -521,13 +521,14 @@ static inline int bond_is_ip6_target_ok(struct in6_addr *addr)
static inline unsigned long slave_oldest_target_arp_rx(struct bonding *bond,
struct slave *slave)
{
+ unsigned long tmp, ret = READ_ONCE(slave->target_last_arp_rx[0]);
int i = 1;
- unsigned long ret = slave->target_last_arp_rx[0];
-
- for (; (i < BOND_MAX_ARP_TARGETS) && bond->params.arp_targets[i]; i++)
- if (time_before(slave->target_last_arp_rx[i], ret))
- ret = slave->target_last_arp_rx[i];

+ for (; (i < BOND_MAX_ARP_TARGETS) && bond->params.arp_targets[i]; i++) {
+ tmp = READ_ONCE(slave->target_last_arp_rx[i]);
+ if (time_before(tmp, ret))
+ ret = tmp;
+ }
return ret;
}

@@ -537,7 +538,7 @@ static inline unsigned long slave_last_rx(struct bonding *bond,
if (bond->params.arp_all_targets == BOND_ARP_TARGETS_ALL)
return slave_oldest_target_arp_rx(bond, slave);

- return slave->last_rx;
+ return READ_ONCE(slave->last_rx);
}

static inline void slave_update_last_tx(struct slave *slave)
--
2.51.0