drivers: usb: usb_dc_sam0: fix memory leak

The usb_dc_sam0 driver is leaking memory when the usb device is detached
using usb_disable().

When a device is detached, the driver does not reliably deallocate the
descriptor bank memory. Therefore, upon the next attach and configure,
another block of memory is allocated. After several connect /
disconnect sequences, the usb interface becomes unresponsive.

This commit adds a static function to release all memory allocated
to the ep descriptors when usb_dc_detach() is called.  Since detach is
called from usb_disable(), this releases the memory when the
interface is disabled.

Avoid calling k_free() if buffer pointer is already
set to NULL.

Fixes #49177

Signed-off-by: Steven Slupsky <[email protected]>

Author: sslupsky

drivers/usb/device/usb_dc_sam0.c

@@ -288,6 +288,31 @@ int usb_dc_attach(void)
 	return 0;
 }
 
+static void usb_dc_release_buffers(void)
+{
+	struct usb_sam0_data *data = usb_sam0_get_data();
+	UsbDeviceDescBank *bank;
+	void *buf;
+
+	/* release the buffers */
+	for (int i = 0; i < ARRAY_SIZE(data->descriptors); i++) {
+		for (int j = 0; j < ARRAY_SIZE(data->descriptors[0].DeviceDescBank); j++) {
+			bank = &data->descriptors[i].DeviceDescBank[j];
+			buf = (void *)bank->ADDR.reg;
+			/*
+			 * We free the ep descriptor memory that was
+			 * allocated in usb_dc_ep_configure().
+			 * Therefore a disabled ep must be reconfigured
+			 * before it can be enabled again.
+			 */
+			if (buf != NULL) {
+				k_free(buf);
+				bank->ADDR.reg = (uintptr_t) NULL;
+			}
+		}
+	}
+}
+
 /* Detach from the bus */
 int usb_dc_detach(void)
 {
@@ -296,6 +321,8 @@ int usb_dc_detach(void)
 	regs->CTRLB.bit.DETACH = 1;
 	usb_sam0_wait_syncbusy();
 
+	usb_dc_release_buffers();
+
 	return 0;
 }