netdev - Re: [PATCH net v2] qlcnic: prevent ->dcb use-after-free on qlcnic_dcb

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Date:   Thu, 22 Dec 2022 14:46:32 +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 net v2] qlcnic: prevent ->dcb use-after-free on
 qlcnic_dcb_enable() failure

On 12/22/22 12:57 PM, Michal Swiatkowski wrote:
> On Thu, Dec 22, 2022 at 10:42:23AM +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 using qlcnic_dcb_free(). This also removes the now
>> unused qlcnic_clear_dcb_ops() helper, which was a simple wrapper around
>> kfree() also causing memory leaks for partially initialized dcb.
>>
>> Found by Linux Verification Center (linuxtesting.org) with the SVACE
>> static analysis tool.
>>
>> Fixes: 3c44bba1d270 ("qlcnic: Disable DCB operations from SR-IOV VFs")
>> Signed-off-by: Daniil Tatianin <d-tatianin@...dex-team.ru>
>> ---
>> Changes since v1:
>> - Add a fixes tag + net as a target
>> - Remove qlcnic_clear_dcb_ops entirely & use qlcnic_dcb_free instead
>> ---
>>   drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c |  9 ++++++++-
>>   drivers/net/ethernet/qlogic/qlcnic/qlcnic_dcb.h       | 10 ++--------
>>   drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c      |  9 ++++++++-
>>   3 files changed, 18 insertions(+), 10 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..774f2c6875ec 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_dcb_free(adapter->dcb);
>> +		adapter->dcb = NULL;
> Small nit, I think qlcnic_dcb_free() already set adapter->dcb to NULL.
Oops, you're right. Thanks for spotting.
> Otherwise, thanks for changing:
> Reviewed-by: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
> 
> Thanks,
> Michal
> 
> [...]
>> -- 
>> 2.25.1