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Wed, 13 Aug 2025 00:49:10 -0700 (PDT) Message-ID: <7641f60d-2d34-4e2c-a467-07cfaba970a9@blackwall.org> Date: Wed, 13 Aug 2025 10:49:05 +0300 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v3] net: bridge: fix soft lockup in br_multicast_query_expired() To: Wang Liang , idosch@nvidia.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org Cc: bridge@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, yuehaibing@huawei.com, zhangchangzhong@huawei.com References: <20250813021054.1643649-1-wangliang74@huawei.com> Content-Language: en-US From: Nikolay Aleksandrov In-Reply-To: <20250813021054.1643649-1-wangliang74@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/13/25 05:10, Wang Liang wrote: > 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: > > __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 > > > 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-wangliang74@huawei.com/ > Link: https://lore.kernel.org/netdev/20250812091818.542238-1-wangliang74@huawei.com/ > Fixes: d902eee43f19 ("bridge: Add multicast count/interval sysfs entries") > Suggested-by: Nikolay Aleksandrov > Signed-off-by: Wang Liang > --- > net/bridge/br_multicast.c | 16 ++++++++++++++++ > net/bridge/br_private.h | 2 ++ > 2 files changed, 18 insertions(+) > Acked-by: Nikolay Aleksandrov