USB: Fix a bug in usb_start_wait_urb

This patch (as941) fixes a bug recently added to the USB synchronous
API.  The status of a completed URB must be preserved separately
across a completion callback.  Also, the actual_length value isn't
available until after the URB has fully completed.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 16 insertions, 10 deletions

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index ad4b956380d2..b6bd05e3d439 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -18,9 +18,17 @@
 #include "hcd.h"        /* for usbcore internals */
 #include "usb.h"
 
+struct api_context {
+        struct completion       done;
+        int                     status;
+};
+
 static void usb_api_blocking_completion(struct urb *urb)
 {
-        complete((struct completion *)urb->context);
+        struct api_context *ctx = urb->context;
+
+        ctx->status = urb->status;
+        complete(&ctx->done);
 }
 
 
@@ -32,20 +40,21 @@ static void usb_api_blocking_completion(struct urb *urb)
  */
 static int usb_start_wait_urb(struct urb *urb, int timeout, int *actual_length)
 { 
-        struct completion done;
+        struct api_context ctx;
         unsigned long expire;
         int retval;
-        int status = urb->status;
 
-        init_completion(&done);         
-        urb->context = &done;
+        init_completion(&ctx.done);
+        urb->context = &ctx;
         urb->actual_length = 0;
         retval = usb_submit_urb(urb, GFP_NOIO);
         if (unlikely(retval))
                 goto out;
 
         expire = timeout ? msecs_to_jiffies(timeout) : MAX_SCHEDULE_TIMEOUT;
-        if (!wait_for_completion_timeout(&done, expire)) {
+        if (!wait_for_completion_timeout(&ctx.done, expire)) {
+                usb_kill_urb(urb);
+                retval = (ctx.status == -ENOENT ? -ETIMEDOUT : ctx.status);
 
                 dev_dbg(&urb->dev->dev,
                         "%s timed out on ep%d%s len=%d/%d\n",
@@ -54,11 +63,8 @@ static int usb_start_wait_urb(struct urb *urb, int timeout, int *actual_length)
                         usb_pipein(urb->pipe) ? "in" : "out",
                         urb->actual_length,
                         urb->transfer_buffer_length);
-
-                usb_kill_urb(urb);
-                retval = status == -ENOENT ? -ETIMEDOUT : status;
         } else
-                retval = status;
+                retval = ctx.status;
 out:
         if (actual_length)
                 *actual_length = urb->actual_length;