Fix an incorrect length value in hid descriptor.

While dumping descriptors of a USB hid device, I saw a weird line:
'Report Descriptor: (length is -1)'

This is because variable 'n' is used to hold a potential negative
integer value even though it's an unsigned int type in function
dump_hid_device. When usb_control_msg() fails, overflow happens.
It will always pass the 'if' statement below and call dump_report_desc(),
where this weird line finally shows up.

To fix it, an int type should be used to avoid overflow.

Signed-off-by: Dingyan Li <18500469033@163.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/lsusb.c b/lsusb.c
index 90825c5..46c9b49 100644
--- a/lsusb.c
+++ b/lsusb.c
@@ -2438,8 +2438,7 @@ static void dump_hid_device(libusb_device_handle *dev,
 			    const struct libusb_interface_descriptor *interface,
 			    const unsigned char *buf)
 {
-	unsigned int i, len;
-	unsigned int n;
+	int i, len;
 	unsigned char dbuf[8192];
 
 	if (buf[1] != LIBUSB_DT_HID)
@@ -2474,13 +2473,13 @@ static void dump_hid_device(libusb_device_handle *dev,
 		if (buf[6+3*i] != LIBUSB_DT_REPORT)
 			continue;
 		len = buf[7+3*i] | (buf[8+3*i] << 8);
-		if (len > (unsigned int)sizeof(dbuf)) {
+		if (len > (int)sizeof(dbuf)) {
 			printf("report descriptor too long\n");
 			continue;
 		}
 		if (libusb_claim_interface(dev, interface->bInterfaceNumber) == 0) {
 			int retries = 4;
-			n = 0;
+			int n = 0;
 			while (n < len && retries--)
 				n = usb_control_msg(dev,
 					 LIBUSB_ENDPOINT_IN | LIBUSB_REQUEST_TYPE_STANDARD
@@ -2495,6 +2494,9 @@ static void dump_hid_device(libusb_device_handle *dev,
 				if (n < len)
 					printf("          Warning: incomplete report descriptor\n");
 				dump_report_desc(dbuf, n);
+			} else {
+				printf("          Warning: can't get report descriptor, %s\n",
+						  libusb_error_name(n));
 			}
 			libusb_release_interface(dev, interface->bInterfaceNumber);
 		} else {