Re: [Intel-wired-lan] [PATCH iwl-next] ice: call mutex_lock() before mutex_unlock() in ice_dcb_rebuild()

[Przemek Kitszel <przemyslaw.kitszel@intel.com>]

On 3/20/26 06:05, Aleksandr Loktionov wrote:
> From: Katarzyna Wieczerzycka <katarzyna.wieczerzycka@intel.com>
> 
> In ice_dcb_rebuild(), the first call to ice_query_port_ets() is checked
> for error, and on failure jumps to the 'dcb_error' label. The error path
> always calls mutex_unlock(&pf->tc_mutex), but at this point in the code
> the mutex has never been locked -- mutex_lock() came after the check.
> 
> Releasing a mutex that was not locked is undefined behaviour and can
> cause a deadlock or crash. Fix this by moving mutex_lock() to before
> the error check, so that 'dcb_error' always pairs with a prior lock.
> 
> Fixes: 242b5e068b25 ("ice: Fix DCB rebuild after reset")
> Signed-off-by: Katarzyna Wieczerzycka <katarzyna.wieczerzycka@intel.com>
> Signed-off-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>

NACK

there is a better fix proposed by community, we are awaiting v2
https://patchew.org/linux/20260223220102.2158611-1-bart.vanassche@linux.dev/20260223220102.2158611-20-bart.vanassche@linux.dev/

> ---
>   drivers/net/ethernet/intel/ice/ice_dcb_lib.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_dcb_lib.c b/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
> index bd77f1c..d516734 100644
> --- a/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
> +++ b/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
> @@ -538,12 +538,11 @@ void ice_dcb_rebuild(struct ice_pf *pf)
>   	int ret;
>   
>   	ret = ice_query_port_ets(pf->hw.port_info, &buf, sizeof(buf), NULL);

the difference is to move mutex_lock() over ice_query_port_ets()

> +	mutex_lock(&pf->tc_mutex);
>   	if (ret) {
>   		dev_err(dev, "Query Port ETS failed\n");
>   		goto dcb_error;
>   	}
>   
> -	mutex_lock(&pf->tc_mutex);
> -
>   	if (!pf->hw.port_info->qos_cfg.is_sw_lldp)
>   		ice_cfg_etsrec_defaults(pf->hw.port_info);
>