When set multicast_query_interval to a large value, the local variable
'time' in br_multicast_send_query() may overflow. If the time is smaller
than jiffies, the timer will expire immediately, and then call mod_timer()
again, which creates a loop and may trigger the following soft lockup
issue.
watchdog: BUG: soft lockup - CPU#1 stuck for 221s! [rb_consumer:66]
CPU: 1 UID: 0 PID: 66 Comm: rb_consumer Not tainted 6.16.0+ #259 PREEMPT(none)
Call Trace:
<IRQ>
__netdev_alloc_skb+0x2e/0x3a0
br_ip6_multicast_alloc_query+0x212/0x1b70
__br_multicast_send_query+0x376/0xac0
br_multicast_send_query+0x299/0x510
br_multicast_query_expired.constprop.0+0x16d/0x1b0
call_timer_fn+0x3b/0x2a0
__run_timers+0x619/0x950
run_timer_softirq+0x11c/0x220
handle_softirqs+0x18e/0x560
__irq_exit_rcu+0x158/0x1a0
sysvec_apic_timer_interrupt+0x76/0x90
</IRQ>
This issue can be reproduced with:
ip link add br0 type bridge
echo 1 > /sys/class/net/br0/bridge/multicast_querier
echo 0xffffffffffffffff >
/sys/class/net/br0/bridge/multicast_query_interval
ip link set dev br0 up
The multicast_startup_query_interval can also cause this issue. Similar to
the commit 99b40610956a ("net: bridge: mcast: add and enforce query
interval minimum"), add check for the query interval maximum to fix this
issue.
Link:
https://lore.kernel.org/netdev/20250806094941.1285944-1-wanglian...@huawei.com/
Link:
https://lore.kernel.org/netdev/20250812091818.542238-1-wanglian...@huawei.com/
Fixes: d902eee43f19 ("bridge: Add multicast count/interval sysfs entries")
Suggested-by: Nikolay Aleksandrov <ra...@blackwall.org>
Signed-off-by: Wang Liang <wanglian...@huawei.com>
---
net/bridge/br_multicast.c | 16 ++++++++++++++++
net/bridge/br_private.h | 2 ++
2 files changed, 18 insertions(+)
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 1377f31b719c..8ce145938b02 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -4818,6 +4818,14 @@ void br_multicast_set_query_intvl(struct
net_bridge_mcast *brmctx,
intvl_jiffies = BR_MULTICAST_QUERY_INTVL_MIN;
}
+ if (intvl_jiffies > BR_MULTICAST_QUERY_INTVL_MAX) {
+ br_info(brmctx->br,
+ "trying to set multicast query interval above maximum,
setting to %lu (%ums)\n",
+ jiffies_to_clock_t(BR_MULTICAST_QUERY_INTVL_MAX),
+ jiffies_to_msecs(BR_MULTICAST_QUERY_INTVL_MAX));
+ intvl_jiffies = BR_MULTICAST_QUERY_INTVL_MAX;
+ }
+
brmctx->multicast_query_interval = intvl_jiffies;
}
@@ -4834,6 +4842,14 @@ void br_multicast_set_startup_query_intvl(struct
net_bridge_mcast *brmctx,
intvl_jiffies = BR_MULTICAST_STARTUP_QUERY_INTVL_MIN;
}
+ if (intvl_jiffies > BR_MULTICAST_STARTUP_QUERY_INTVL_MAX) {
+ br_info(brmctx->br,
+ "trying to set multicast startup query interval above
maximum, setting to %lu (%ums)\n",
+
jiffies_to_clock_t(BR_MULTICAST_STARTUP_QUERY_INTVL_MAX),
+ jiffies_to_msecs(BR_MULTICAST_STARTUP_QUERY_INTVL_MAX));
+ intvl_jiffies = BR_MULTICAST_STARTUP_QUERY_INTVL_MAX;
+ }
+
brmctx->multicast_startup_query_interval = intvl_jiffies;
}
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index b159aae594c0..8de0904b9627 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -31,6 +31,8 @@
#define BR_MULTICAST_DEFAULT_HASH_MAX 4096
#define BR_MULTICAST_QUERY_INTVL_MIN msecs_to_jiffies(1000)
#define BR_MULTICAST_STARTUP_QUERY_INTVL_MIN BR_MULTICAST_QUERY_INTVL_MIN
+#define BR_MULTICAST_QUERY_INTVL_MAX msecs_to_jiffies(86400000) /* 24 hours */
+#define BR_MULTICAST_STARTUP_QUERY_INTVL_MAX BR_MULTICAST_QUERY_INTVL_MAX
#define BR_HWDOM_MAX BITS_PER_LONG
--
2.33.0
