linux-hardening - [PATCH] platform/surface: Split memcpy() of struct ssam

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Message-Id: <20220927004011.1942739-1-keescook@chromium.org>
Date:   Mon, 26 Sep 2022 17:40:11 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Maximilian Luz <luzmaximilian@...il.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH] platform/surface: Split memcpy() of struct ssam_event 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: Maximilian Luz <luzmaximilian@...il.com>
Cc: Hans de Goede <hdegoede@...hat.com>
Cc: Mark Gross <markgross@...nel.org>
Cc: platform-driver-x86@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/platform/surface/surface_acpi_notify.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/surface/surface_acpi_notify.c b/drivers/platform/surface/surface_acpi_notify.c
index 44e317970557..50500e562963 100644
--- a/drivers/platform/surface/surface_acpi_notify.c
+++ b/drivers/platform/surface/surface_acpi_notify.c
@@ -355,7 +355,8 @@ static u32 san_evt_bat_nf(struct ssam_event_notifier *nf,
 	INIT_DELAYED_WORK(&work->work, san_evt_bat_workfn);
 	work->dev = d->dev;
 
-	memcpy(&work->event, event, sizeof(struct ssam_event) + event->length);
+	work->event = *event;
+	memcpy(work->event.data, event->data, event->length);
 
 	queue_delayed_work(san_wq, &work->work, delay);
 	return SSAM_NOTIF_HANDLED;
-- 
2.34.1