linux-kernel - [PATCH][next] usb: dwc2: Use flex_array

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Date:   Tue, 11 Jan 2022 01:55:13 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Minas Harutyunyan <hminas@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] usb: dwc2: Use flex_array_size() helper

Make use of the flex_array_size() helper to calculate the size of a
flexible array member within an enclosing structure.

This helper offers defense-in-depth against potential integer
overflows, while at the same time makes it explicitly clear that
we are dealing with a flexible array member.

Link: https://github.com/KSPP/linux/issues/160
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/usb/dwc2/hcd.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index f63a27d11fac..2c21498662cd 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -4054,8 +4054,9 @@ struct dwc2_tt *dwc2_host_get_tt_info(struct dwc2_hsotg *hsotg, void *context,
 			 * For single_tt we need one schedule.  For multi_tt
 			 * we need one per port.
 			 */
-			bitmap_size = DWC2_ELEMENTS_PER_LS_BITMAP *
-				      sizeof(dwc_tt->periodic_bitmaps[0]);
+			bitmap_size =
+				flex_array_size(dwc_tt, periodic_bitmaps,
+						DWC2_ELEMENTS_PER_LS_BITMAP);
 			if (urb->dev->tt->multi)
 				bitmap_size *= urb->dev->tt->hub->maxchild;
 
-- 
2.27.0