linux-kernel - Re: [PATCH] wifi: iwlwifi: ptp: Fix potential race condition in PTP removal

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Message-ID: <aW5p4jVhcz70ZFl4@horms.kernel.org>
Date: Mon, 19 Jan 2026 17:29:06 +0000
From: Simon Horman <horms@...nel.org>
To: Junjie Cao <junjie.cao@...el.com>
Cc: Miri Korenblit <miriam.rachel.korenblit@...el.com>,
	Johannes Berg <johannes.berg@...el.com>,
	linux-wireless@...r.kernel.org,
	Richard Cochran <richardcochran@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yedidya Benshimol <yedidya.ben.shimol@...el.com>,
	Avraham Stern <avraham.stern@...el.com>,
	Daniel Gabay <daniel.gabay@...el.com>,
	Krishnanand Prabhu <krishnanand.prabhu@...el.com>,
	Luca Coelho <luciano.coelho@...el.com>,
	Gregory Greenman <gregory.greenman@...el.com>,
	stable@...r.kernel.org, Yao Zi <ziyao@...root.org>,
	Benjamin Berg <benjamin.berg@...el.com>
Subject: Re: [PATCH] wifi: iwlwifi: ptp: Fix potential race condition in PTP
 removal

+ Yao Zi and Benjamin Berg

On Fri, Jan 16, 2026 at 12:15:29AM +0800, Junjie Cao wrote:
> iwl_mvm_ptp_remove() and iwl_mld_ptp_remove() call
> cancel_delayed_work_sync() only after ptp_clock_unregister() and after
> partially clearing ptp_data state.
> 
> This creates a race where the delayed work (iwl_mvm_ptp_work /
> iwl_mld_ptp_work) can run while teardown is in progress and observe a
> partially modified PTP state. In addition, the work may re-arm itself,
> extending the teardown window and risking execution after driver
> resources have been released.
> 
> Move cancel_delayed_work_sync() before ptp_clock_unregister() to ensure
> the delayed work is fully stopped before any PTP cleanup begins. This
> follows the standard pattern used by other Intel PTP drivers such as
> e1000e, igb, ixgbe, and ice.
> 
> Fixes: d1e879ec600f ("wifi: iwlwifi: add iwlmld sub-driver")
> Fixes: 1595ecce1cf3 ("wifi: iwlwifi: mvm: add support for PTP HW clock (PHC)")
> Cc: stable@...r.kernel.org
> Signed-off-by: Junjie Cao <junjie.cao@...el.com>

Thinking out loud: The two cited commits were introduced in
the same upstream release - v6.4 - so from a backporting PoV
it seems reasonable to address these issues in one patch.
Though I do think it would be best to think of these
as two things and thus warranting two patches.

That notwithstanding, the changes look good to me.

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

Context left intact below for the benefit of Yao Zi and Benjamin Berg.

> ---
>  drivers/net/wireless/intel/iwlwifi/mld/ptp.c | 2 +-
>  drivers/net/wireless/intel/iwlwifi/mvm/ptp.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/mld/ptp.c b/drivers/net/wireless/intel/iwlwifi/mld/ptp.c
> index 231920425c06..b40182320801 100644
> --- a/drivers/net/wireless/intel/iwlwifi/mld/ptp.c
> +++ b/drivers/net/wireless/intel/iwlwifi/mld/ptp.c
> @@ -319,10 +319,10 @@ void iwl_mld_ptp_remove(struct iwl_mld *mld)
>  			       mld->ptp_data.ptp_clock_info.name,
>  			       ptp_clock_index(mld->ptp_data.ptp_clock));
>  
> +		cancel_delayed_work_sync(&mld->ptp_data.dwork);
>  		ptp_clock_unregister(mld->ptp_data.ptp_clock);
>  		mld->ptp_data.ptp_clock = NULL;
>  		mld->ptp_data.last_gp2 = 0;
>  		mld->ptp_data.wrap_counter = 0;
> -		cancel_delayed_work_sync(&mld->ptp_data.dwork);
>  	}
>  }
> diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/ptp.c b/drivers/net/wireless/intel/iwlwifi/mvm/ptp.c
> index 1da6260e238c..2b01ca36a1b5 100644
> --- a/drivers/net/wireless/intel/iwlwifi/mvm/ptp.c
> +++ b/drivers/net/wireless/intel/iwlwifi/mvm/ptp.c
> @@ -325,11 +325,11 @@ void iwl_mvm_ptp_remove(struct iwl_mvm *mvm)
>  			       mvm->ptp_data.ptp_clock_info.name,
>  			       ptp_clock_index(mvm->ptp_data.ptp_clock));
>  
> +		cancel_delayed_work_sync(&mvm->ptp_data.dwork);
>  		ptp_clock_unregister(mvm->ptp_data.ptp_clock);
>  		mvm->ptp_data.ptp_clock = NULL;
>  		memset(&mvm->ptp_data.ptp_clock_info, 0,
>  		       sizeof(mvm->ptp_data.ptp_clock_info));
>  		mvm->ptp_data.last_gp2 = 0;
> -		cancel_delayed_work_sync(&mvm->ptp_data.dwork);
>  	}
>  }
> -- 
> 2.43.0
>