[PATCH] USB: EHCI: fix conflation of buf == 0 with len == 0
When the ehci-hcd driver prepares a control URB, it tests for a
zero-length data stage by looking at the transfer_dma value instead of
the transfer_buffer_length. (In fact it does this even for non-control
URBs, which is an additional aspect of the same bug.)
However, under certain circumstances it's possible for transfer_dma to
be 0 while transfer_buffer_length is non-zero. This can happen when a
freshly allocated page (mapped to address 0 and marked Copy-On-Write,
but never written to) is used as the source buffer for an OUT transfer.
This patch (as598) fixes the problem.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index bf03ec0..9b13bf2 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -514,18 +514,18 @@
qtd->urb = urb;
qtd_prev->hw_next = QTD_NEXT (qtd->qtd_dma);
list_add_tail (&qtd->qtd_list, head);
+
+ /* for zero length DATA stages, STATUS is always IN */
+ if (len == 0)
+ token |= (1 /* "in" */ << 8);
}
/*
* data transfer stage: buffer setup
*/
- if (likely (len > 0))
- buf = urb->transfer_dma;
- else
- buf = 0;
+ buf = urb->transfer_dma;
- /* for zero length DATA stages, STATUS is always IN */
- if (!buf || is_input)
+ if (is_input)
token |= (1 /* "in" */ << 8);
/* else it's already initted to "out" pid (0 << 8) */
@@ -572,7 +572,7 @@
* control requests may need a terminating data "status" ack;
* bulk ones may need a terminating short packet (zero length).
*/
- if (likely (buf != 0)) {
+ if (likely (urb->transfer_buffer_length != 0)) {
int one_more = 0;
if (usb_pipecontrol (urb->pipe)) {