Re: [PATCH net v2] bridge: cfm: reject invalid CCM interval at configuration time

Simon Horman
2026-04-06T14:15:35Z

On Sat, Apr 04, 2026 at 05:03:24PM -0700, Xiang Mei wrote:
> ccm_tx_work_expired() re-arms itself via queue_delayed_work() using
> the configured exp_interval converted by interval_to_us(). When
> exp_interval is BR_CFM_CCM_INTERVAL_NONE or out of range,
> interval_to_us() returns 0, causing the worker to fire immediately in
> a tight loop that allocates skbs until OOM.
>
> Fix this by validating exp_interval at configuration time:
>
> - Constrain IFLA_BRIDGE_CFM_CC_CONFIG_EXP_INTERVAL to [1, 7] in the
> netlink policy so userspace cannot set an invalid value.
>
> - Reject starting CCM TX in br_cfm_cc_ccm_tx() when exp_interval has
> not yet been configured (defaults to 0 from kzalloc).
>
> Fixes: a806ad8ee2aa ("bridge: cfm: Kernel space implementation of CFM. CCM frame TX added.")
> Reported-by: Weiming Shi <bestswngs@gmail.com>
> Signed-off-by: Xiang Mei <xmei5@asu.edu>
> ---
> v2: Move validation out of the datapath and into configuration

Thanks for the update.

Reviewed-by: Simon Horman <horms@kernel.org>

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