netdev - Re: [PATCH net 2/4] ice: Don't process extts if PTP is disabled

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Date: Tue, 25 Jun 2024 10:57:38 -0700
From: "Nelson, Shannon" <shannon.nelson@....com>
To: Tony Nguyen <anthony.l.nguyen@...el.com>, davem@...emloft.net,
 kuba@...nel.org, pabeni@...hat.com, edumazet@...gle.com,
 netdev@...r.kernel.org
Cc: Jacob Keller <jacob.e.keller@...el.com>, richardcochran@...il.com,
 Przemek Kitszel <przemyslaw.kitszel@...el.com>,
 Karol Kolacinski <karol.kolacinski@...el.com>,
 Simon Horman <horms@...nel.org>,
 Pucha Himasekhar Reddy <himasekharx.reddy.pucha@...el.com>
Subject: Re: [PATCH net 2/4] ice: Don't process extts if PTP is disabled

On 6/25/2024 10:02 AM, Tony Nguyen wrote:
> From: Jacob Keller <jacob.e.keller@...el.com>
> 
> The ice_ptp_extts_event() function can race with ice_ptp_release() and
> result in a NULL pointer dereference which leads to a kernel panic.
> 
> Panic occurs because the ice_ptp_extts_event() function calls
> ptp_clock_event() with a NULL pointer. The ice driver has already
> released the PTP clock by the time the interrupt for the next external
> timestamp event occurs.
> 
> To fix this, modify the ice_ptp_extts_event() function to check the
> PTP state and bail early if PTP is not ready.
> 
> Fixes: 172db5f91d5f ("ice: add support for auxiliary input/output pins")
> Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@...el.com>
> Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
> Signed-off-by: Karol Kolacinski <karol.kolacinski@...el.com>
> Reviewed-by: Simon Horman <horms@...nel.org>
> Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@...el.com> (A Contingent worker at Intel)
> Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
> ---
>   drivers/net/ethernet/intel/ice/ice_ptp.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_ptp.c b/drivers/net/ethernet/intel/ice/ice_ptp.c
> index d8ff9f26010c..0500ced1adf8 100644
> --- a/drivers/net/ethernet/intel/ice/ice_ptp.c
> +++ b/drivers/net/ethernet/intel/ice/ice_ptp.c
> @@ -1559,6 +1559,10 @@ void ice_ptp_extts_event(struct ice_pf *pf)
>          u8 chan, tmr_idx;
>          u32 hi, lo;
> 
> +       /* Don't process timestamp events if PTP is not ready */
> +       if (pf->ptp.state != ICE_PTP_READY)
> +               return;
> +

If this is a potential race problem, is there some sort of locking that 
assures this stays true while running through your for-loop below here?

sln

>          tmr_idx = hw->func_caps.ts_func_info.tmr_index_owned;
>          /* Event time is captured by one of the two matched registers
>           *      GLTSYN_EVNT_L: 32 LSB of sampled time event
> --
> 2.41.0
> 
>