linux-hardening - Re: [PATCH] s390/qeth: Split memcpy() of struct qeth_ipacmd_addr

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Message-ID: <23b905f8-2836-8879-fe9f-9521e0f8674e@linux.ibm.com>
Date:   Tue, 27 Sep 2022 13:54:27 +0200
From:   Alexandra Winter <wintera@...ux.ibm.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Kees Cook <keescook@...omium.org>
Cc:     Wenjia Zhang <wenjia@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] s390/qeth: Split memcpy() of struct
 qeth_ipacmd_addr_change flexible array



On 27.09.22 03:16, Gustavo A. R. Silva wrote:
> On Mon, Sep 26, 2022 at 05:39:53PM -0700, Kees Cook wrote:
>> To work around a misbehavior of the compiler's ability to see into
>> composite flexible array structs (as detailed in the coming memcpy()
>> hardening series[1]), split the memcpy() of the header and the payload
>> so no false positive run-time overflow warning will be generated.
>>
>> [1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org/
>>
>> Cc: Alexandra Winter <wintera@...ux.ibm.com>
>> Cc: Wenjia Zhang <wenjia@...ux.ibm.com>
>> Cc: Heiko Carstens <hca@...ux.ibm.com>
>> Cc: Vasily Gorbik <gor@...ux.ibm.com>
>> Cc: Alexander Gordeev <agordeev@...ux.ibm.com>
>> Cc: Christian Borntraeger <borntraeger@...ux.ibm.com>
>> Cc: Sven Schnelle <svens@...ux.ibm.com>
>> Cc: linux-s390@...r.kernel.org
>> Cc: netdev@...r.kernel.org
>> Signed-off-by: Kees Cook <keescook@...omium.org>
> 
> Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> 
> Thanks!
> --
> Gustavo
> 
Reviewed-by: Alexandra Winter <wintera@...ux.ibm.com>

Thank you
Alexandra
>> ---
>>  drivers/s390/net/qeth_l2_main.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c
>> index 2d4436cbcb47..0ce635b7b472 100644
>> --- a/drivers/s390/net/qeth_l2_main.c
>> +++ b/drivers/s390/net/qeth_l2_main.c
>> @@ -1530,8 +1530,8 @@ static void qeth_addr_change_event(struct qeth_card *card,
>>  	else
>>  		INIT_DELAYED_WORK(&data->dwork, qeth_l2_dev2br_worker);
>>  	data->card = card;
>> -	memcpy(&data->ac_event, hostevs,
>> -			sizeof(struct qeth_ipacmd_addr_change) + extrasize);
>> +	data->ac_event = *hostevs;
>> +	memcpy(data->ac_event.entry, hostevs->entry, extrasize);
>>  	queue_delayed_work(card->event_wq, &data->dwork, 0);
>>  }
>>  
>> -- 
>> 2.34.1
>>