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authorAlan Stern <stern@rowland.harvard.edu>2005-11-03 11:44:49 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2006-01-04 13:48:29 -0800
commit6912354a895fcd234155273fe8838a0d83259a9b (patch)
tree6dca4969dda3fb177c62f18b12bfb6d2be4bb567
parent959eea2191e8d74b16ef019b0f4bf875c14f4547 (diff)
[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>
-rw-r--r--drivers/usb/host/ehci-q.c14
1 files changed, 7 insertions, 7 deletions
diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index bf03ec0d8ee..9b13bf2fa98 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -514,18 +514,18 @@ qh_urb_transaction (
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 @@ qh_urb_transaction (
* 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)) {