linux-kernel - Re: [PATCH v1] qlcnic: prevent ->dcb use-after-free on qlcnic_dcb

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Message-ID: <8c49acd6-7195-caaf-425c-b9ed9290423d@yandex-team.ru>
Date:   Wed, 21 Dec 2022 10:47:29 +0300
From:   Daniil Tatianin <d-tatianin@...dex-team.ru>
To:     Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
Cc:     Shahed Shaikh <shshaikh@...vell.com>,
        Manish Chopra <manishc@...vell.com>,
        GR-Linux-NIC-Dev@...vell.com,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] qlcnic: prevent ->dcb use-after-free on
 qlcnic_dcb_enable() failure

On 12/20/22 4:32 PM, Michal Swiatkowski wrote:
> On Tue, Dec 20, 2022 at 03:56:49PM +0300, Daniil Tatianin wrote:
>> adapter->dcb would get silently freed inside qlcnic_dcb_enable() in
>> case qlcnic_dcb_attach() would return an error, which always happens
>> under OOM conditions. This would lead to use-after-free because both
>> of the existing callers invoke qlcnic_dcb_get_info() on the obtained
>> pointer, which is potentially freed at that point.
>>
>> Propagate errors from qlcnic_dcb_enable(), and instead free the dcb
>> pointer at callsite.
>>
>> Found by Linux Verification Center (linuxtesting.org) with the SVACE
>> static analysis tool.
>>
>> Signed-off-by: Daniil Tatianin <d-tatianin@...dex-team.ru>
> 
> Please add Fix tag and net as target (net-next is close till the end of
> this year)
>
Sorry, I'll include a fixes tag.
Could you please explain what I would have to do to add net as target?
>> ---
>>   drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c | 9 ++++++++-
>>   drivers/net/ethernet/qlogic/qlcnic/qlcnic_dcb.h       | 5 ++---
>>   drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c      | 9 ++++++++-
>>   3 files changed, 18 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c
>> index dbb800769cb6..465f149d94d4 100644
>> --- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c
>> +++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c
>> @@ -2505,7 +2505,14 @@ int qlcnic_83xx_init(struct qlcnic_adapter *adapter)
>>   		goto disable_mbx_intr;
>>   
>>   	qlcnic_83xx_clear_function_resources(adapter);
>> -	qlcnic_dcb_enable(adapter->dcb);
>> +
>> +	err = qlcnic_dcb_enable(adapter->dcb);
>> +	if (err) {
>> +		qlcnic_clear_dcb_ops(adapter->dcb);
>> +		adapter->dcb = NULL;
>> +		goto disable_mbx_intr;
>> +	}
> 
> Maybe I miss sth but it looks like there can be memory leak.
> For example if error in attach happen after allocating of dcb->cfg.
> Isn't it better to call qlcnic_dcb_free instead of qlcnic_clear_dcb_ops?
I think you're right, if attach fails midway then we might leak cfg or 
something else.
I'll use qlcnic_dcb_free() instead and completely remove 
qlcnic_clear_dcb_ops() as it
seems to be unused and relies on dcb being in a very specific state.
>> +
>>   	qlcnic_83xx_initialize_nic(adapter, 1);
>>   	qlcnic_dcb_get_info(adapter->dcb);
>>   
>> diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_dcb.h b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_dcb.h
>> index 7519773eaca6..e1460f9c38bf 100644
>> --- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_dcb.h
>> +++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_dcb.h
>> @@ -112,9 +112,8 @@ static inline void qlcnic_dcb_init_dcbnl_ops(struct qlcnic_dcb *dcb)
>>   		dcb->ops->init_dcbnl_ops(dcb);
>>   }
>>   
>> -static inline void qlcnic_dcb_enable(struct qlcnic_dcb *dcb)
>> +static inline int qlcnic_dcb_enable(struct qlcnic_dcb *dcb)
>>   {
>> -	if (dcb && qlcnic_dcb_attach(dcb))
>> -		qlcnic_clear_dcb_ops(dcb);
>> +	return dcb ? qlcnic_dcb_attach(dcb) : 0;
>>   }
>>   #endif
>> diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
>> index 28476b982bab..36ba15fc9776 100644
>> --- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
>> +++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
>> @@ -2599,7 +2599,14 @@ qlcnic_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>>   			 "Device does not support MSI interrupts\n");
>>   
>>   	if (qlcnic_82xx_check(adapter)) {
>> -		qlcnic_dcb_enable(adapter->dcb);
>> +		err = qlcnic_dcb_enable(adapter->dcb);
>> +		if (err) {
>> +			qlcnic_clear_dcb_ops(adapter->dcb);
>> +			adapter->dcb = NULL;
>> +			dev_err(&pdev->dev, "Failed to enable DCB\n");
>> +			goto err_out_free_hw;
>> +		}
>> +
>>   		qlcnic_dcb_get_info(adapter->dcb);
>>   		err = qlcnic_setup_intr(adapter);
>>   
>> -- 
>> 2.25.1
>>