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

From: Simon Horman <[email-masked]>
Date: Mon, 6 Apr 2026 15:15:31 +0100

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 <[email-masked]>
> Signed-off-by: Xiang Mei <[email-masked]>
> ---
> v2: Move validation out of the datapath and into configuration

Thanks for the update.

Reviewed-by: Simon Horman <[email-masked]>

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