xhci: Avoid infinite loop when sg urb requires too many trbs

Currently prepare_ring() returns -ENOMEM if the urb won't fit into a
single ring segment.  usb_sg_wait() treats this error as a temporary
condition and will keep retrying until something else goes wrong.

The number of retries should be limited in usb_sg_wait(), but also
prepare_ring() should not return an error code that suggests it might
be worth retrying.  Change it to -EINVAL.

Reported-by: jidanni@jidanni.org
References: http://bugs.debian.org/733907
Fixes: 35773dac5f86 ('usb: xhci: Link TRB must not occur within a USB payload burst')
Cc: stable <stable@vger.kernel.org> # 3.12
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 09b2b551be72b2ed63d673339e779dcef638c0c4..a0b248c345266e470441bba48247aea00b22fc13 100644 (file)
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -3000,7 +3000,7 @@ static int prepare_ring(struct xhci_hcd *xhci, struct xhci_ring *ep_ring,
                        if (num_trbs >= TRBS_PER_SEGMENT) {
                                xhci_err(xhci, "Too many fragments %d, max %d\n",
                                                num_trbs, TRBS_PER_SEGMENT - 1);
-                               return -ENOMEM;
+                               return -EINVAL;
                        }
 
                        nop_cmd = cpu_to_le32(TRB_TYPE(TRB_TR_NOOP) |