[PATCH 2/3] xhci: Avoid infinite loop when sg urb requires too manytrbs

[Ben Hutchings]

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@xxxxxxxxxxx
References: http://bugs.debian.org/733907
Fixes: 35773dac5f86 ('usb: xhci: Link TRB must not occur within a USB payload burst')
Cc: stable <stable@xxxxxxxxxxxxxxx> # 3.12
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
---
 drivers/usb/host/xhci-ring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index d05f61dc8359..2afaf15009e8 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2978,7 +2978,7 @@ 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;
 			}
 			xhci_dbg(xhci, "Insert no-op TRBs at 0x%llx\n",
 					(unsigned long long)
-- 
1.8.3.3


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