[PATCH 5.10 064/121] bonding: fix data-races around agg_select_timer

Greg Kroah-Hartman
2022-02-21T09:20:09Z

From: Eric Dumazet <edumazet@google.com>

commit 9ceaf6f76b203682bb6100e14b3d7da4c0bedde8 upstream.

syzbot reported that two threads might write over agg_select_timer
at the same time. Make agg_select_timer atomic to fix the races.

BUG: KCSAN: data-race in bond_3ad_initiate_agg_selection / bond_3ad_state_machine_handler

read to 0xffff8881242aea90 of 4 bytes by task 1846 on cpu 1:
bond_3ad_state_machine_handler+0x99/0x2810 drivers/net/bonding/bond_3ad.c:2317
process_one_work+0x3f6/0x960 kernel/workqueue.c:2307
worker_thread+0x616/0xa70 kernel/workqueue.c:2454
kthread+0x1bf/0x1e0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30

write to 0xffff8881242aea90 of 4 bytes by task 25910 on cpu 0:
bond_3ad_initiate_agg_selection+0x18/0x30 drivers/net/bonding/bond_3ad.c:1998
bond_open+0x658/0x6f0 drivers/net/bonding/bond_main.c:3967
__dev_open+0x274/0x3a0 net/core/dev.c:1407
dev_open+0x54/0x190 net/core/dev.c:1443
bond_enslave+0xcef/0x3000 drivers/net/bonding/bond_main.c:1937
do_set_master net/core/rtnetlink.c:2532 [inline]
do_setlink+0x94f/0x2500 net/core/rtnetlink.c:2736
__rtnl_newlink net/core/rtnetlink.c:3414 [inline]
rtnl_newlink+0xfeb/0x13e0 net/core/rtnetlink.c:3529
rtnetlink_rcv_msg+0x745/0x7e0 net/core/rtnetlink.c:5594
netlink_rcv_skb+0x14e/0x250 net/netlink/af_netlink.c:2494
rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:5612
netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
netlink_unicast+0x602/0x6d0 net/netlink/af_netlink.c:1343
netlink_sendmsg+0x728/0x850 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:705 [inline]
sock_sendmsg net/socket.c:725 [inline]
____sys_sendmsg+0x39a/0x510 net/socket.c:2413
___sys_sendmsg net/socket.c:2467 [inline]
__sys_sendmsg+0x195/0x230 net/socket.c:2496
__do_sys_sendmsg net/socket.c:2505 [inline]
__se_sys_sendmsg net/socket.c:2503 [inline]
__x64_sys_sendmsg+0x42/0x50 net/socket.c:2503
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

value changed: 0x00000050 -> 0x0000004f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 25910 Comm: syz-executor.1 Tainted: G W 5.17.0-rc4-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Jay Vosburgh <j.vosburgh@gmail.com>
Cc: Veaceslav Falico <vfalico@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/bonding/bond_3ad.c | 30 +++++++++++++++++++++++++-----
include/net/bond_3ad.h | 2 +-
2 files changed, 26 insertions(+), 6 deletions(-)

--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -223,7 +223,7 @@ static inline int __check_agg_selection_
if (bond == NULL)
return 0;

- return BOND_AD_INFO(bond).agg_select_timer ? 1 : 0;
+ return atomic_read(&BOND_AD_INFO(bond).agg_select_timer) ? 1 : 0;
}

/**
@@ -1976,7 +1976,7 @@ static void ad_marker_response_received(
*/
void bond_3ad_initiate_agg_selection(struct bonding *bond, int timeout)
{
- BOND_AD_INFO(bond).agg_select_timer = timeout;
+ atomic_set(&BOND_AD_INFO(bond).agg_select_timer, timeout);
}

/**
@@ -2260,6 +2260,28 @@ void bond_3ad_update_ad_actor_settings(s
}

/**
+ * bond_agg_timer_advance - advance agg_select_timer
+ * @bond: bonding structure
+ *
+ * Return true when agg_select_timer reaches 0.
+ */
+static bool bond_agg_timer_advance(struct bonding *bond)
+{
+ int val, nval;
+
+ while (1) {
+ val = atomic_read(&BOND_AD_INFO(bond).agg_select_timer);
+ if (!val)
+ return false;
+ nval = val - 1;
+ if (atomic_cmpxchg(&BOND_AD_INFO(bond).agg_select_timer,
+ val, nval) == val)
+ break;
+ }
+ return nval == 0;
+}
+
+/**
* bond_3ad_state_machine_handler - handle state machines timeout
* @work: work context to fetch bonding struct to work on from
*
@@ -2294,9 +2316,7 @@ void bond_3ad_state_machine_handler(stru
if (!bond_has_slaves(bond))
goto re_arm;

- /* check if agg_select_timer timer after initialize is timed out */
- if (BOND_AD_INFO(bond).agg_select_timer &&
- !(--BOND_AD_INFO(bond).agg_select_timer)) {
+ if (bond_agg_timer_advance(bond)) {
slave = bond_first_slave_rcu(bond);
port = slave ? &(SLAVE_AD_INFO(slave)->port) : NULL;

--- a/include/net/bond_3ad.h
+++ b/include/net/bond_3ad.h
@@ -262,7 +262,7 @@ struct ad_system {
struct ad_bond_info {
struct ad_system system; /* 802.3ad system structure */
struct bond_3ad_stats stats;
- u32 agg_select_timer; /* Timer to select aggregator after all adapter's hand shakes */
+ atomic_t agg_select_timer; /* Timer to select aggregator after all adapter's hand shakes */
u16 aggregator_identifier;
};