[PATCH 4.19 197/219] usbip: Fix receive error in vhci-hcd when using scatter-gather

[Greg Kroah-Hartman]

From: Suwan Kim <suwan.kim027@xxxxxxxxx>

commit d986294ee55d719562b20aabe15a39bf8f863415 upstream.

When vhci uses SG and receives data whose size is smaller than SG
buffer size, it tries to receive more data even if it acutally
receives all the data from the server. If then, it erroneously adds
error event and triggers connection shutdown.

vhci-hcd should check if it received all the data even if there are
more SG entries left. So, check if it receivces all the data from
the server in for_each_sg() loop.

Fixes: ea44d190764b ("usbip: Implement SG support to vhci-hcd and stub driver")
Reported-by: Marek Marczykowski-GÃrecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Tested-by: Marek Marczykowski-GÃrecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Suwan Kim <suwan.kim027@xxxxxxxxx>
Acked-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20191213023055.19933-2-suwan.kim027@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/usbip/usbip_common.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/usb/usbip/usbip_common.c
+++ b/drivers/usb/usbip/usbip_common.c
@@ -727,6 +727,9 @@ int usbip_recv_xbuff(struct usbip_device
 
 			copy -= recv;
 			ret += recv;
+
+			if (!copy)
+				break;
 		}
 
 		if (ret != size)