Re: [PATCH net] bridge: mrp: reject zero test interval to avoid OOM panic

[Nikolay Aleksandrov <razor@blackwall.org>]

On 27/03/2026 13:34, Simon Horman wrote:
> On Wed, Mar 25, 2026 at 08:24:38PM -0700, Xiang Mei wrote:
>> br_mrp_start_test() and br_mrp_start_in_test() accept the user-supplied
>> interval value from netlink without validation. When interval is 0,
>> usecs_to_jiffies(0) yields 0, causing the delayed work
>> (br_mrp_test_work_expired / br_mrp_in_test_work_expired) to reschedule
>> itself with zero delay. This creates a tight loop on system_percpu_wq
>> that allocates and transmits MRP test frames at maximum rate, exhausting
>> all system memory and causing a kernel panic via OOM deadlock.
> 
> I would suspect the primary outcome of this problem is high CPU consumption
> rather than memory exhaustion. Is there a reason to expect that
> the transmitted fames can't be consumed as fast as they are created?
> 

+1
More so with CAP_NET_ADMIN you can cause all sorts of OOM and high-cpu usage
conditions. This is a configuration error and OOM doesn't lead to panic unless
instructed to. I don't think this is worth changing at all.

>>
>> The same zero-interval issue applies to br_mrp_start_in_test_parse()
>> for interconnect test frames.
>>
>> Use NLA_POLICY_MIN(NLA_U32, 1) in the nla_policy tables for both
>> IFLA_BRIDGE_MRP_START_TEST_INTERVAL and
>> IFLA_BRIDGE_MRP_START_IN_TEST_INTERVAL, so zero is rejected at the
>> netlink attribute parsing layer before the value ever reaches the
>> workqueue scheduling code. This is consistent with how other bridge
>> subsystems (br_fdb, br_mst) enforce range constraints on netlink
>> attributes.
>>
>> Fixes: 7ab1748e4ce6 ("bridge: mrp: Extend MRP netlink interface for configuring MRP interconnect")
> 
> I think you also want
> 
> Fixes: 20f6a05ef635 ("bridge: mrp: Rework the MRP netlink interface")
> 
> As highlighted by AI review.
> 
>> Reported-by: Weiming Shi <bestswngs@gmail.com>
>> Signed-off-by: Xiang Mei <xmei5@asu.edu>
> 
> ...