staging: gpib: Fix Oops after disconnect in agilent usb

If the agilent usb dongle is disconnected subsequent calls to the
driver cause a NULL dereference Oops as the bus_interface
is set to NULL on disconnect.

This problem was introduced by setting usb_dev from the bus_interface
for dev_xxx messages.

Previously bus_interface was checked for NULL only in the functions
directly calling usb_fill_bulk_urb or usb_control_msg.

Check for valid bus_interface on all interface entry points
and return -ENODEV if it is NULL.

Fixes: fbae709 ("staging: gpib: Update messaging and usb_device refs in agilent_usb")
Cc: stable <[email protected]>
Signed-off-by: Dave Penkler <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: dpenkler

drivers/staging/gpib/agilent_82357a/agilent_82357a.c

@@ -427,7 +427,7 @@ static int agilent_82357a_read(gpib_board_t *board, uint8_t *buffer, size_t leng
 {
 	int retval;
 	struct agilent_82357a_priv *a_priv = board->private_data;
-	struct usb_device *usb_dev = interface_to_usbdev(a_priv->bus_interface);
+	struct usb_device *usb_dev;
 	u8 *out_data, *in_data;
 	int out_data_length, in_data_length;
 	int bytes_written, bytes_read;
@@ -438,6 +438,10 @@ static int agilent_82357a_read(gpib_board_t *board, uint8_t *buffer, size_t leng
 
 	*nbytes = 0;
 	*end = 0;
+
+	if (!a_priv->bus_interface)
+		return -ENODEV;
+	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	out_data_length = 0x9;
 	out_data = kmalloc(out_data_length, GFP_KERNEL);
 	if (!out_data)
@@ -534,7 +538,7 @@ static ssize_t agilent_82357a_generic_write(gpib_board_t *board, uint8_t *buffer
 {
 	int retval;
 	struct agilent_82357a_priv *a_priv = board->private_data;
-	struct usb_device *usb_dev = interface_to_usbdev(a_priv->bus_interface);
+	struct usb_device *usb_dev;
 	u8 *out_data = NULL;
 	u8 *status_data = NULL;
 	int out_data_length;
@@ -545,6 +549,10 @@ static ssize_t agilent_82357a_generic_write(gpib_board_t *board, uint8_t *buffer
 	struct agilent_82357a_register_pairlet read_reg;
 
 	*bytes_written = 0;
+	if (!a_priv->bus_interface)
+		return -ENODEV;
+
+	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	out_data_length = length + 0x8;
 	out_data = kmalloc(out_data_length, GFP_KERNEL);
 	if (!out_data)
@@ -697,9 +705,13 @@ int agilent_82357a_take_control_internal(gpib_board_t *board, int synchronous)
 
 static int agilent_82357a_take_control(gpib_board_t *board, int synchronous)
 {
+	struct agilent_82357a_priv *a_priv = board->private_data;
 	const int timeout = 10;
 	int i;
 
+	if (!a_priv->bus_interface)
+		return -ENODEV;
+
 /* It looks like the 9914 does not handle tcs properly.
  *  See comment above tms9914_take_control_workaround() in
  *  drivers/gpib/tms9914/tms9914_aux.c
@@ -723,10 +735,14 @@ static int agilent_82357a_take_control(gpib_board_t *board, int synchronous)
 static int agilent_82357a_go_to_standby(gpib_board_t *board)
 {
 	struct agilent_82357a_priv *a_priv = board->private_data;
-	struct usb_device *usb_dev = interface_to_usbdev(a_priv->bus_interface);
+	struct usb_device *usb_dev;
 	struct agilent_82357a_register_pairlet write;
 	int retval;
 
+	if (!a_priv->bus_interface)
+		return -ENODEV;
+
+	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	write.address = AUXCR;
 	write.value = AUX_GTS;
 	retval = agilent_82357a_write_registers(a_priv, &write, 1);
@@ -739,11 +755,15 @@ static int agilent_82357a_go_to_standby(gpib_board_t *board)
 static void agilent_82357a_request_system_control(gpib_board_t *board, int request_control)
 {
 	struct agilent_82357a_priv *a_priv = board->private_data;
-	struct usb_device *usb_dev = interface_to_usbdev(a_priv->bus_interface);
+	struct usb_device *usb_dev;
 	struct agilent_82357a_register_pairlet writes[2];
 	int retval;
 	int i = 0;
 
+	if (!a_priv->bus_interface)
+		return; // -ENODEV;
+
+	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	/* 82357B needs bit to be set in 9914 AUXCR register */
 	writes[i].address = AUXCR;
 	if (request_control) {
@@ -767,10 +787,14 @@ static void agilent_82357a_request_system_control(gpib_board_t *board, int reque
 static void agilent_82357a_interface_clear(gpib_board_t *board, int assert)
 {
 	struct agilent_82357a_priv *a_priv = board->private_data;
-	struct usb_device *usb_dev = interface_to_usbdev(a_priv->bus_interface);
+	struct usb_device *usb_dev;
 	struct agilent_82357a_register_pairlet write;
 	int retval;
 
+	if (!a_priv->bus_interface)
+		return; // -ENODEV;
+
+	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	write.address = AUXCR;
 	write.value = AUX_SIC;
 	if (assert) {
@@ -785,10 +809,14 @@ static void agilent_82357a_interface_clear(gpib_board_t *board, int assert)
 static void agilent_82357a_remote_enable(gpib_board_t *board, int enable)
 {
 	struct agilent_82357a_priv *a_priv = board->private_data;
-	struct usb_device *usb_dev = interface_to_usbdev(a_priv->bus_interface);
+	struct usb_device *usb_dev;
 	struct agilent_82357a_register_pairlet write;
 	int retval;
 
+	if (!a_priv->bus_interface)
+		return; //-ENODEV;
+
+	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	write.address = AUXCR;
 	write.value = AUX_SRE;
 	if (enable)
@@ -804,6 +832,8 @@ static int agilent_82357a_enable_eos(gpib_board_t *board, uint8_t eos_byte, int
 {
 	struct agilent_82357a_priv *a_priv = board->private_data;
 
+	if (!a_priv->bus_interface)
+		return -ENODEV;
 	if (compare_8_bits == 0)
 		return -EOPNOTSUPP;
 
@@ -822,10 +852,13 @@ static void agilent_82357a_disable_eos(gpib_board_t *board)
 static unsigned int agilent_82357a_update_status(gpib_board_t *board, unsigned int clear_mask)
 {
 	struct agilent_82357a_priv *a_priv = board->private_data;
-	struct usb_device *usb_dev = interface_to_usbdev(a_priv->bus_interface);
+	struct usb_device *usb_dev;
 	struct agilent_82357a_register_pairlet address_status, bus_status;
 	int retval;
 
+	if (!a_priv->bus_interface)
+		return -ENODEV;
+	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	board->status &= ~clear_mask;
 	if (a_priv->is_cic)
 		set_bit(CIC_NUM, &board->status);
@@ -885,6 +918,9 @@ static int agilent_82357a_primary_address(gpib_board_t *board, unsigned int addr
 	struct agilent_82357a_register_pairlet write;
 	int retval;
 
+	if (!a_priv->bus_interface)
+		return -ENODEV;
+	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	// put primary address in address0
 	write.address = ADR;
 	write.value = address & ADDRESS_MASK;
@@ -906,11 +942,14 @@ static int agilent_82357a_secondary_address(gpib_board_t *board, unsigned int ad
 static int agilent_82357a_parallel_poll(gpib_board_t *board, uint8_t *result)
 {
 	struct agilent_82357a_priv *a_priv = board->private_data;
-	struct usb_device *usb_dev = interface_to_usbdev(a_priv->bus_interface);
+	struct usb_device *usb_dev;
 	struct agilent_82357a_register_pairlet writes[2];
 	struct agilent_82357a_register_pairlet read;
 	int retval;
 
+	if (!a_priv->bus_interface)
+		return -ENODEV;
+	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	// execute parallel poll
 	writes[0].address = AUXCR;
 	writes[0].value = AUX_CS | AUX_RPP;
@@ -975,11 +1014,14 @@ static void agilent_82357a_return_to_local(gpib_board_t *board)
 static int agilent_82357a_line_status(const gpib_board_t *board)
 {
 	struct agilent_82357a_priv *a_priv = board->private_data;
-	struct usb_device *usb_dev = interface_to_usbdev(a_priv->bus_interface);
+	struct usb_device *usb_dev;
 	struct agilent_82357a_register_pairlet bus_status;
 	int retval;
 	int status = ValidALL;
 
+	if (!a_priv->bus_interface)
+		return -ENODEV;
+	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	bus_status.address = BSR;
 	retval = agilent_82357a_read_registers(a_priv, &bus_status, 1, 0);
 	if (retval) {
@@ -1025,10 +1067,13 @@ static unsigned short nanosec_to_fast_talker_bits(unsigned int *nanosec)
 static unsigned int agilent_82357a_t1_delay(gpib_board_t *board, unsigned int nanosec)
 {
 	struct agilent_82357a_priv *a_priv = board->private_data;
-	struct usb_device *usb_dev = interface_to_usbdev(a_priv->bus_interface);
+	struct usb_device *usb_dev;
 	struct agilent_82357a_register_pairlet write;
 	int retval;
 
+	if (!a_priv->bus_interface)
+		return -ENODEV;
+	usb_dev = interface_to_usbdev(a_priv->bus_interface);
 	write.address = FAST_TALKER_T1;
 	write.value = nanosec_to_fast_talker_bits(&nanosec);
 	retval = agilent_82357a_write_registers(a_priv, &write, 1);