[PATCH 5.4 20/88] bonding: make tx_rebalance_counter an atomic

Greg Kroah-Hartman
2021-12-13T09:55:59Z

From: Eric Dumazet <edumazet@google.com>

commit dac8e00fb640e9569cdeefd3ce8a75639e5d0711 upstream.

KCSAN reported a data-race [1] around tx_rebalance_counter
which can be accessed from different contexts, without
the protection of a lock/mutex.

[1]
BUG: KCSAN: data-race in bond_alb_init_slave / bond_alb_monitor

write to 0xffff888157e8ca24 of 4 bytes by task 7075 on cpu 0:
bond_alb_init_slave+0x713/0x860 drivers/net/bonding/bond_alb.c:1613
bond_enslave+0xd94/0x3010 drivers/net/bonding/bond_main.c:1949
do_set_master net/core/rtnetlink.c:2521 [inline]
__rtnl_newlink net/core/rtnetlink.c:3475 [inline]
rtnl_newlink+0x1298/0x13b0 net/core/rtnetlink.c:3506
rtnetlink_rcv_msg+0x745/0x7e0 net/core/rtnetlink.c:5571
netlink_rcv_skb+0x14e/0x250 net/netlink/af_netlink.c:2491
rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:5589
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x5fc/0x6c0 net/netlink/af_netlink.c:1345
netlink_sendmsg+0x6e1/0x7d0 net/netlink/af_netlink.c:1916
sock_sendmsg_nosec net/socket.c:704 [inline]
sock_sendmsg net/socket.c:724 [inline]
____sys_sendmsg+0x39a/0x510 net/socket.c:2409
___sys_sendmsg net/socket.c:2463 [inline]
__sys_sendmsg+0x195/0x230 net/socket.c:2492
__do_sys_sendmsg net/socket.c:2501 [inline]
__se_sys_sendmsg net/socket.c:2499 [inline]
__x64_sys_sendmsg+0x42/0x50 net/socket.c:2499
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888157e8ca24 of 4 bytes by task 1082 on cpu 1:
bond_alb_monitor+0x8f/0xc00 drivers/net/bonding/bond_alb.c:1511
process_one_work+0x3fc/0x980 kernel/workqueue.c:2298
worker_thread+0x616/0xa70 kernel/workqueue.c:2445
kthread+0x2c7/0x2e0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30

value changed: 0x00000001 -> 0x00000064

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1082 Comm: kworker/u4:3 Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bond1 bond_alb_monitor

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/bonding/bond_alb.c | 14 ++++++++------
include/net/bond_alb.h | 2 +-
2 files changed, 9 insertions(+), 7 deletions(-)

--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -1514,14 +1514,14 @@ void bond_alb_monitor(struct work_struct
struct slave *slave;

if (!bond_has_slaves(bond)) {
- bond_info->tx_rebalance_counter = 0;
+ atomic_set(&bond_info->tx_rebalance_counter, 0);
bond_info->lp_counter = 0;
goto re_arm;
}

rcu_read_lock();

- bond_info->tx_rebalance_counter++;
+ atomic_inc(&bond_info->tx_rebalance_counter);
bond_info->lp_counter++;

/* send learning packets */
@@ -1543,7 +1543,7 @@ void bond_alb_monitor(struct work_struct
}

/* rebalance tx traffic */
- if (bond_info->tx_rebalance_counter >= BOND_TLB_REBALANCE_TICKS) {
+ if (atomic_read(&bond_info->tx_rebalance_counter) >= BOND_TLB_REBALANCE_TICKS) {
bond_for_each_slave_rcu(bond, slave, iter) {
tlb_clear_slave(bond, slave, 1);
if (slave == rcu_access_pointer(bond->curr_active_slave)) {
@@ -1553,7 +1553,7 @@ void bond_alb_monitor(struct work_struct
bond_info->unbalanced_load = 0;
}
}
- bond_info->tx_rebalance_counter = 0;
+ atomic_set(&bond_info->tx_rebalance_counter, 0);
}

if (bond_info->rlb_enabled) {
@@ -1623,7 +1623,8 @@ int bond_alb_init_slave(struct bonding *
tlb_init_slave(slave);

/* order a rebalance ASAP */
- bond->alb_info.tx_rebalance_counter = BOND_TLB_REBALANCE_TICKS;
+ atomic_set(&bond->alb_info.tx_rebalance_counter,
+ BOND_TLB_REBALANCE_TICKS);

if (bond->alb_info.rlb_enabled)
bond->alb_info.rlb_rebalance = 1;
@@ -1660,7 +1661,8 @@ void bond_alb_handle_link_change(struct
rlb_clear_slave(bond, slave);
} else if (link == BOND_LINK_UP) {
/* order a rebalance ASAP */
- bond_info->tx_rebalance_counter = BOND_TLB_REBALANCE_TICKS;
+ atomic_set(&bond_info->tx_rebalance_counter,
+ BOND_TLB_REBALANCE_TICKS);
if (bond->alb_info.rlb_enabled) {
bond->alb_info.rlb_rebalance = 1;
/* If the updelay module parameter is smaller than the
--- a/include/net/bond_alb.h
+++ b/include/net/bond_alb.h
@@ -126,7 +126,7 @@ struct tlb_slave_info {
struct alb_bond_info {
struct tlb_client_info *tx_hashtbl; /* Dynamically allocated */
u32 unbalanced_load;
- int tx_rebalance_counter;
+ atomic_t tx_rebalance_counter;
int lp_counter;
/* -------- rlb parameters -------- */
int rlb_enabled;