[Intel-wired-lan] [PATCH v1 iwl-net] ice: fix potential NULL pointer deref in error path of ice_set_ringparam()

[Greenwalt, Paul]

On 2/20/2026 12:04 PM, Loktionov, Aleksandr wrote:
> 
> 
>> -----Original Message-----
>> From: Kohei Enju <kohei at enjuk.jp>
>> Sent: Friday, February 20, 2026 7:40 PM
>> To: intel-wired-lan at lists.osuosl.org; netdev at vger.kernel.org
>> Cc: Nguyen, Anthony L <anthony.l.nguyen at intel.com>; Kitszel,
>> Przemyslaw <przemyslaw.kitszel at intel.com>; Andrew Lunn
>> <andrew+netdev at lunn.ch>; David S. Miller <davem at davemloft.net>; Eric
>> Dumazet <edumazet at google.com>; Jakub Kicinski <kuba at kernel.org>; Paolo
>> Abeni <pabeni at redhat.com>; Loktionov, Aleksandr
>> <aleksandr.loktionov at intel.com>; Alice Michael
>> <alice.michael at intel.com>; Greenwalt, Paul <paul.greenwalt at intel.com>;
>> Fijalkowski, Maciej <maciej.fijalkowski at intel.com>;
>> kohei.enju at gmail.com; Kohei Enju <kohei at enjuk.jp>
>> Subject: [PATCH v1 iwl-net] ice: fix potential NULL pointer deref in
>> error path of ice_set_ringparam()
>>
>> ice_set_ringparam nullifies tstamp_ring of temporary tx_rings, without
>> clearing ICE_TX_RING_FLAGS_TXTIME bit.
>> When ICE_TX_RING_FLAGS_TXTIME is set and the subsequent
>> ice_setup_tx_ring() call fails, a NULL pointer dereference could
>> happen in the unwinding sequence:
>>
>> ice_clean_tx_ring()
>> -> ice_is_txtime_cfg() == true (ICE_TX_RING_FLAGS_TXTIME is set)
>> -> ice_free_tx_tstamp_ring()
>>   -> ice_free_tstamp_ring()
>>     -> tstamp_ring->desc (NULL deref)
>>
>> Clear ICE_TX_RING_FLAGS_TXTIME bit to avoid the potential issue.
>>
>> Note that this potential issue is found by manual code review.
>> Compile test only since unfortunately I don't have E830 devices.
>>
>> Fixes: ccde82e90946 ("ice: add E830 Earliest TxTime First Offload
>> support")
> If it's a fix, shouldn't it go to net?
> 

Thank you for identifying this bug. However, clearing
ICE_TX_RING_FLAGS_TXTIME before ice_setup_tx_ring() will break TxTime
offload on the success path.

ice_setup_tx_ring() doesn't read this flag, but ice_up() (called later)
needs it set to reallocate the tstamp ring for the new ring size. Your
change would silently disable TxTime after any successful ring parameter
change.

The fix should clear the flag only in the error path:

if (err) {
	while (i--) {
		clear_bit(ICE_TX_RING_FLAGS_TXTIME, tx_rings[i].flags);
		ice_clean_tx_ring(&tx_rings[i]);
	}
	vfree(tx_rings);
	goto done;
}

Also, per Alex's comment, please target 'net'.

Thanks,
Paul

>> Signed-off-by: Kohei Enju <kohei at enjuk.jp>
>> ---
>>  drivers/net/ethernet/intel/ice/ice_ethtool.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/net/ethernet/intel/ice/ice_ethtool.c
>> b/drivers/net/ethernet/intel/ice/ice_ethtool.c
>> index 7f769a90dde1..5ed86648d0d6 100644
>> --- a/drivers/net/ethernet/intel/ice/ice_ethtool.c
>> +++ b/drivers/net/ethernet/intel/ice/ice_ethtool.c
>> @@ -3290,6 +3290,7 @@ ice_set_ringparam(struct net_device *netdev,
>> struct ethtool_ringparam *ring,
>>  		tx_rings[i].desc = NULL;
>>  		tx_rings[i].tx_buf = NULL;
>>  		tx_rings[i].tstamp_ring = NULL;
>> +		clear_bit(ICE_TX_RING_FLAGS_TXTIME, tx_rings[i].flags);
>>  		tx_rings[i].tx_tstamps = &pf->ptp.port.tx;
>>  		err = ice_setup_tx_ring(&tx_rings[i]);
> If ice_setup_tx_ring() internally reads ICE_TX_RING_FLAGS_TXTIME to decide whether to allocate the tstamp_ring, then clearing the bit first means ice_setup_tx_ring() skips TxTime setup even on success - leaving TxTime silently broken after ice_set_ringparam() completes normally. The crash is fixed on the error path, but I'm afraid a functional regression is introduced on the success path.
> Please correct me if I'm wrong.
> 
> Thank you
> Alex
> 
>>  		if (err) {
>> --
>> 2.51.0
>