[PATCH v3] gpib: Fix memory leak in ni_usb_init()

[Zilin Guan]

In ni_usb_init(), if ni_usb_setup_init() fails, the function returns
-EFAULT without freeing the allocated writes buffer, leading to a
memory leak.

Additionally, ni_usb_setup_init() returns 0 on failure, which causes
ni_usb_init() to return -EFAULT, an inappropriate error code for this
situation.

Fix the leak by freeing writes in the error path. Modify
ni_usb_setup_init() to return -EINVAL on failure and propagate this
error code in ni_usb_init().

Fixes: 4e127de14fa7 ("staging: gpib: Add National Instruments USB GPIB driver")
Suggested-by: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
Suggested-by: Dave Penkler <dpenkler@xxxxxxxxx>
Co-developed-by: Jianhao Xu <jianhao.xu@xxxxxxxxxx>
Signed-off-by: Jianhao Xu <jianhao.xu@xxxxxxxxxx>
Signed-off-by: Zilin Guan <zilin@xxxxxxxxxx>
---
Changes in v3:
- Enable ni_usb_setup_init() to return negative error codes on failure.
- Remove "staging" prefix based on current file path.

Changes in v2:
- Use early return to simplify error handling logic.

 drivers/gpib/ni_usb/ni_usb_gpib.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/gpib/ni_usb/ni_usb_gpib.c b/drivers/gpib/ni_usb/ni_usb_gpib.c
index 1f8412de9fa3..52fb76b48467 100644
--- a/drivers/gpib/ni_usb/ni_usb_gpib.c
+++ b/drivers/gpib/ni_usb/ni_usb_gpib.c
@@ -1780,7 +1780,7 @@ static int ni_usb_setup_init(struct gpib_board *board, struct ni_usb_register *w
 	i++;
 	if (i > NUM_INIT_WRITES) {
 		dev_err(&usb_dev->dev, "bug!, buffer overrun, i=%i\n", i);
-		return 0;
+		return -EINVAL;
 	}
 	return i;
 }
@@ -1799,10 +1799,12 @@ static int ni_usb_init(struct gpib_board *board)
 		return -ENOMEM;
 
 	writes_len = ni_usb_setup_init(board, writes);
-	if (writes_len)
-		retval = ni_usb_write_registers(ni_priv, writes, writes_len, &ibsta);
-	else
-		return -EFAULT;
+	if (writes_len < 0) {
+		kfree(writes);
+		return writes_len;
+	}
+
+	retval = ni_usb_write_registers(ni_priv, writes, writes_len, &ibsta);
 	kfree(writes);
 	if (retval) {
 		dev_err(&usb_dev->dev, "register write failed, retval=%i\n", retval);
-- 
2.34.1