netdev - Re: [PATCH] aquantia: Fix "ethtool -S" crash when adapter down.

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Message-Id: <20170504.125113.569969253752966231.davem@davemloft.net>
Date:   Thu, 04 May 2017 12:51:13 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     LinoSanfilippo@....de
Cc:     Pavel.Belous@...antia.com, netdev@...r.kernel.org,
        darcari@...hat.com
Subject: Re: [PATCH] aquantia: Fix "ethtool -S" crash when adapter down.

From: Lino Sanfilippo <LinoSanfilippo@....de>
Date: Thu, 4 May 2017 18:48:12 +0200

> Hi Pavel,
> 
> On 04.05.2017 18:33, Pavel Belous wrote:
>> From: Pavel Belous <pavel.belous@...antia.com>
>> 
>> This patch fixes the crash that happens when driver tries to collect statistics
>> from already released "aq_vec" object.
>> 
>> Fixes: 97bde5c4f909 ("net: ethernet: aquantia: Support for NIC-specific code")
>> Signed-off-by: Pavel Belous <pavel.belous@...antia.com>
>> ---
>>  drivers/net/ethernet/aquantia/atlantic/aq_nic.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
>> index cdb0299..3a32573 100644
>> --- a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
>> +++ b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
>> @@ -755,7 +755,7 @@ void aq_nic_get_stats(struct aq_nic_s *self, u64 *data)
>>  	count = 0U;
>>  
>>  	for (i = 0U, aq_vec = self->aq_vec[0];
>> -		self->aq_vecs > i; ++i, aq_vec = self->aq_vec[i]) {
>> +		aq_vec && self->aq_vecs > i; ++i, aq_vec = self->aq_vec[i]) {
>>  		data += count;
>>  		aq_vec_get_sw_stats(aq_vec, data, &count);
>>  	}
>> @@ -961,6 +961,7 @@ void aq_nic_free_hot_resources(struct aq_nic_s *self)
>>  	for (i = AQ_DIMOF(self->aq_vec); i--;) {
>>  		if (self->aq_vec[i])
>>  			aq_vec_free(self->aq_vec[i]);
>> +			self->aq_vec[i] = NULL;
>>  	}
>>  
>>  err_exit:;
>> 
> 
> if the driver does not support statistics when the interface is down, would not it be clearer
> to check if netif_running() in get_stats() instead?

Yes, much cleaner.

Much better would be to have a cached software copy so that statistics
can be reported regardless of whether the device is down or not.