Re: [PATCH net v2] bridge: mrp: reject zero test interval to avoid OOM panic

[Nikolay Aleksandrov <razor@blackwall.org>]

On 28/03/2026 08:30, 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.
> 
> 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: 20f6a05ef635 ("bridge: mrp: Rework the MRP netlink interface")
> Fixes: 7ab1748e4ce6 ("bridge: mrp: Extend MRP netlink interface for configuring MRP interconnect")
> Reported-by: Weiming Shi <bestswngs@gmail.com>
> Signed-off-by: Xiang Mei <xmei5@asu.edu>
> ---
>   net/bridge/br_mrp_netlink.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/bridge/br_mrp_netlink.c b/net/bridge/br_mrp_netlink.c
> index ce6f63c77cc0..86f0e75d6e34 100644
> --- a/net/bridge/br_mrp_netlink.c
> +++ b/net/bridge/br_mrp_netlink.c
> @@ -196,7 +196,7 @@ static const struct nla_policy
>   br_mrp_start_test_policy[IFLA_BRIDGE_MRP_START_TEST_MAX + 1] = {
>   	[IFLA_BRIDGE_MRP_START_TEST_UNSPEC]	= { .type = NLA_REJECT },
>   	[IFLA_BRIDGE_MRP_START_TEST_RING_ID]	= { .type = NLA_U32 },
> -	[IFLA_BRIDGE_MRP_START_TEST_INTERVAL]	= { .type = NLA_U32 },
> +	[IFLA_BRIDGE_MRP_START_TEST_INTERVAL]	= NLA_POLICY_MIN(NLA_U32, 1),
>   	[IFLA_BRIDGE_MRP_START_TEST_MAX_MISS]	= { .type = NLA_U32 },
>   	[IFLA_BRIDGE_MRP_START_TEST_PERIOD]	= { .type = NLA_U32 },
>   	[IFLA_BRIDGE_MRP_START_TEST_MONITOR]	= { .type = NLA_U32 },
> @@ -316,7 +316,7 @@ static const struct nla_policy
>   br_mrp_start_in_test_policy[IFLA_BRIDGE_MRP_START_IN_TEST_MAX + 1] = {
>   	[IFLA_BRIDGE_MRP_START_IN_TEST_UNSPEC]	= { .type = NLA_REJECT },
>   	[IFLA_BRIDGE_MRP_START_IN_TEST_IN_ID]	= { .type = NLA_U32 },
> -	[IFLA_BRIDGE_MRP_START_IN_TEST_INTERVAL]	= { .type = NLA_U32 },
> +	[IFLA_BRIDGE_MRP_START_IN_TEST_INTERVAL]	= NLA_POLICY_MIN(NLA_U32, 1),
>   	[IFLA_BRIDGE_MRP_START_IN_TEST_MAX_MISS]	= { .type = NLA_U32 },
>   	[IFLA_BRIDGE_MRP_START_IN_TEST_PERIOD]	= { .type = NLA_U32 },
>   };

Alright, let's limit them :-)

Acked-by: Nikolay Aleksandrov <razor@blackwall.org>