usb: xhci: address off-by-one in xhci_num_trbs_free()

Reduce the number of do-while loops by 1. The number of loops should be
number of segment + 1, the +1 is in case deq and enq are on the same
segment. But due to the use of a do-while loop, the expression is
evaluated after executing the loop, thus the loop is executed 1 extra
time.

Changing the do-while loop expression from "<=" to "<", reduces the loop
amount by 1. The expression "<=" would also work if it was a while loop
instead of a do-while loop.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20240429140245.3955523-6-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 3cc5c70d54c723a5acc001a9e9ae4b83779c9bca..0a7c70ae5edc3dded6394ce511699313cc377827 100644 (file)
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -308,7 +308,7 @@ static unsigned int xhci_num_trbs_free(struct xhci_hcd *xhci, struct xhci_ring *
                free += last_on_seg - enq;
                enq_seg = enq_seg->next;
                enq = enq_seg->trbs;
-       } while (i++ <= ring->num_segs);
+       } while (i++ < ring->num_segs);
 
        return free;
 }