[PATCH] s390/qeth: Split memcpy() of struct qeth_ipacmd_addr_change flexible array

[PATCH] s390/qeth: Split memcpy() of struct qeth_ipacmd_addr_change flexible array

[Kees Cook]

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@linux.ibm.com>
Cc: Wenjia Zhang <wenjia@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: linux-s390@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 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

Re: [PATCH] s390/qeth: Split memcpy() of struct qeth_ipacmd_addr_change flexible array

[Gustavo A. R. Silva]

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@linux.ibm.com>
> Cc: Wenjia Zhang <wenjia@linux.ibm.com>
> Cc: Heiko Carstens <hca@linux.ibm.com>
> Cc: Vasily Gorbik <gor@linux.ibm.com>
> Cc: Alexander Gordeev <agordeev@linux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
> Cc: Sven Schnelle <svens@linux.ibm.com>
> Cc: linux-s390@vger.kernel.org
> Cc: netdev@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks!
--
Gustavo

> ---
>  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
> 

Re: [PATCH] s390/qeth: Split memcpy() of struct qeth_ipacmd_addr_change flexible array

[Alexandra Winter]

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@linux.ibm.com>
>> Cc: Wenjia Zhang <wenjia@linux.ibm.com>
>> Cc: Heiko Carstens <hca@linux.ibm.com>
>> Cc: Vasily Gorbik <gor@linux.ibm.com>
>> Cc: Alexander Gordeev <agordeev@linux.ibm.com>
>> Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
>> Cc: Sven Schnelle <svens@linux.ibm.com>
>> Cc: linux-s390@vger.kernel.org
>> Cc: netdev@vger.kernel.org
>> Signed-off-by: Kees Cook <keescook@chromium.org>
> 
> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> 
> Thanks!
> --
> Gustavo
> 
Reviewed-by: Alexandra Winter <wintera@linux.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
>>

Re: [PATCH] s390/qeth: Split memcpy() of struct qeth_ipacmd_addr_change flexible array

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 26 Sep 2022 17:39:53 -0700 you 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/
> 
> [...]

Here is the summary with links:
  - s390/qeth: Split memcpy() of struct qeth_ipacmd_addr_change flexible array
    https://git.kernel.org/netdev/net-next/c/8f1e1658d365

You are awesome, thank you!
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