linux-kernel - [PATCH v2] USB: gadget: dummy

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Message-Id: <20221109084450.2181848-1-gregkh@linuxfoundation.org>
Date:   Wed,  9 Nov 2022 09:44:50 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-usb@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        Jakob Koschel <jakobkoschel@...il.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH v2] USB: gadget: dummy_hcd: switch char * to u8 *

The function handle_control_request() casts the urb buffer to a char *,
and then treats it like a unsigned char buffer when assigning data to
it.  On some architectures, "char" is really signed, so let's just
properly set this pointer to a u8 to take away any potential problems as
that's what is really wanted here.

Use put_unaligned_le16() to copy the full 16bits into the buffer,
it's not a problem just yet as only 7 bits are being used here, but this
protects us when/if the USB spec changes in the future to define more of
these bits.

Cc: Felipe Balbi <balbi@...nel.org>
Cc: Jakob Koschel <jakobkoschel@...il.com>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Ira Weiny <ira.weiny@...el.com>
Cc: Alan Stern <stern@...land.harvard.edu>
Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
v2: - use put_unaligned_le16() on Linus's recommendation as a simpler and
      more obvious way to describe the data being copied here.
    - update device: comment based on Alan's review

 drivers/usb/gadget/udc/dummy_hcd.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c
index 899ac9f9c279..7c59c20c8623 100644
--- a/drivers/usb/gadget/udc/dummy_hcd.c
+++ b/drivers/usb/gadget/udc/dummy_hcd.c
@@ -1740,13 +1740,13 @@ static int handle_control_request(struct dummy_hcd *dum_hcd, struct urb *urb,
 		if (setup->bRequestType == Dev_InRequest
 				|| setup->bRequestType == Intf_InRequest
 				|| setup->bRequestType == Ep_InRequest) {
-			char *buf;
+			u8 *buf;
 			/*
-			 * device: remote wakeup, selfpowered
+			 * device: remote wakeup, selfpowered, LTM, U1, or U2
 			 * interface: nothing
 			 * endpoint: halt
 			 */
-			buf = (char *)urb->transfer_buffer;
+			buf = urb->transfer_buffer;
 			if (urb->transfer_buffer_length > 0) {
 				if (setup->bRequestType == Ep_InRequest) {
 					ep2 = find_endpoint(dum, w_index);
@@ -1755,10 +1755,9 @@ static int handle_control_request(struct dummy_hcd *dum_hcd, struct urb *urb,
 						break;
 					}
 					buf[0] = ep2->halted;
-				} else if (setup->bRequestType ==
-					   Dev_InRequest) {
-					buf[0] = (u8)dum->devstatus;
-				} else
+				} else if (setup->bRequestType == Dev_InRequest)
+					put_unaligned_le16(dum->devstatus, buf);
+				else
 					buf[0] = 0;
 			}
 			if (urb->transfer_buffer_length > 1)
-- 
2.38.1