[PATCH v2] usbip: Fix free of unallocated memory in vhci tx

[Suwan Kim <suwan.kim027@gmail.com>]

iso_buffer should be set to NULL after use and free in the while loop.
In the case of isochronous URB in the while loop, iso_buffer is
allocated and after sending it to server, buffer is deallocated. And
then, if the next URB in the while loop is not a isochronous pipe,
iso_buffer still holds the previously deallocated buffer address and
kfree tries to free wrong buffer address.

Fixes: ea44d190764b ("usbip: Implement SG support to vhci-hcd and stub driver")
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
---
v1 - v2: Move the setting NULL after kfree() and add the comment
---
 drivers/usb/usbip/vhci_tx.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/usbip/vhci_tx.c b/drivers/usb/usbip/vhci_tx.c
index c3803785f6ef..0ae40a13a9fe 100644
--- a/drivers/usb/usbip/vhci_tx.c
+++ b/drivers/usb/usbip/vhci_tx.c
@@ -147,7 +147,10 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
 		}
 
 		kfree(iov);
+		/* This is only for isochronous case */
 		kfree(iso_buffer);
+		iso_buffer = NULL;
+
 		usbip_dbg_vhci_tx("send txdata\n");
 
 		total_size += txsize;
-- 
2.20.1