usbip: Accept arbitrarily long scatter-gather list

Fixes issue where memory will fail to be allocated for larger bulk
transfers, ~1 MB or more. This occurs because userland libraries, such
as libusb, send the entire USB data buffer when SG support is detected.
The assumption is that the driver knows how to properly split the data
up before sending it out.

By hardcoding a limit, bigger transfers that exceed the SG tablesize
limit of 32 will be unable to use SG. This results in an attempt to
allocate contiguous pages which, unsurprisingly, will fail too and
returns an ENOMEM. It looks like other drivers that support SG allow for
any length of SG lists. Accepting any SG size allows the driver to
properly handle large bulk transfer situations.

Tested bulk read and write operations using the following devices:

 - Logitech Webcam Pro 9000 - USB 2.0
 - SanDisk Ultra - USB 3.0
 - Logitech M500s Mouse

Signed-off-by: Jason Long <jasonlongball@gmail.com>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20241218161344.202637-1-jasonlongball@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index b03e5021c25bd538f93dd9f0d99a24e5443e51f6..2f722849dfc9ff64b8801c56beca3cde49184f31 100644 (file)
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c
@@ -1161,12 +1161,8 @@ static int vhci_setup(struct usb_hcd *hcd)
                hcd->self.root_hub->speed = USB_SPEED_SUPER_PLUS;
        }
 
-       /*
-        * Support SG.
-        * sg_tablesize is an arbitrary value to alleviate memory pressure
-        * on the host.
-        */
-       hcd->self.sg_tablesize = 32;
+       /* accept arbitrarily long scatter-gather lists */
+       hcd->self.sg_tablesize = ~0;
        hcd->self.no_sg_constraint = 1;
 
        return 0;