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

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: 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>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Link: https://lore.kernel.org/r/20220927003953.1942442-1-keescook@chromium.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c
index 2d4436c..0ce635b 100644 (file)
--- 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);
 }