[PATCH v2 43/63] net: qede: Use memset_startat() for counters

[Kees Cook]

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Use memset_startat() so memset() doesn't get confused about writing
beyond the destination member that is intended to be the starting point
of zeroing through the end of the struct.

The old code was doing the wrong thing: it starts from the second member
and writes beyond int_info, clobbering qede_lock:

struct qede_dev {
	...
        struct qed_int_info             int_info;

        /* Smaller private variant of the RTNL lock */
        struct mutex                    qede_lock;
	...

struct qed_int_info {
        struct msix_entry       *msix;
        u8                      msix_cnt;

        /* This should be updated by the protocol driver */
        u8                      used_cnt;
};

Cc: Ariel Elior <aelior@xxxxxxxxxxx>
Cc: GR-everest-linux-l2@xxxxxxxxxxx
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 drivers/net/ethernet/qlogic/qede/qede_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/qlogic/qede/qede_main.c b/drivers/net/ethernet/qlogic/qede/qede_main.c
index d400e9b235bf..0ed9a0c8452c 100644
--- a/drivers/net/ethernet/qlogic/qede/qede_main.c
+++ b/drivers/net/ethernet/qlogic/qede/qede_main.c
@@ -2419,7 +2419,7 @@ static int qede_load(struct qede_dev *edev, enum qede_load_mode mode,
 	goto out;
 err4:
 	qede_sync_free_irqs(edev);
-	memset(&edev->int_info.msix_cnt, 0, sizeof(struct qed_int_info));
+	memset_startat(&edev->int_info, 0, msix_cnt);
 err3:
 	qede_napi_disable_remove(edev);
 err2:
-- 
2.30.2