usb: wusbcore: fix potential double list_del on urb dequeue

This patch locks rpipe->seg_lock around the entire transfer segment
cleanup loop in wa_urb_dequeue instead of just one case of the switch
statement.  This fixes a race between __wa_xfer_delayed_run and
wa_urb_dequeue where a transfer segment in the WA_SEG_DELAYED state
could be removed from the rpipe seg_list twice leading to memory
corruption.  It also switches the spin_lock call to use the non-irqsave
version since the xfer->lock is already held and irqs already disabled.

Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/usb/wusbcore/wa-xfer.c b/drivers/usb/wusbcore/wa-xfer.c
index 404ce81b286c..6e0d377d437c 100644
--- a/drivers/usb/wusbcore/wa-xfer.c
+++ b/drivers/usb/wusbcore/wa-xfer.c
@@ -1974,6 +1974,11 @@ int wa_urb_dequeue(struct wahc *wa, struct urb *urb, int status)
                 goto out_unlock;        /* setup(), enqueue_b() completes */
         /* Ok, the xfer is in flight already, it's been setup and submitted.*/
         xfer_abort_pending = __wa_xfer_abort(xfer) >= 0;
+        /*
+         * grab the rpipe->seg_lock here to prevent racing with
+         * __wa_xfer_delayed_run.
+         */
+        spin_lock(&rpipe->seg_lock);
         for (cnt = 0; cnt < xfer->segs; cnt++) {
                 seg = xfer->seg[cnt];
                 pr_debug("%s: xfer id 0x%08X#%d status = %d\n",
@@ -1994,10 +1999,8 @@ int wa_urb_dequeue(struct wahc *wa, struct urb *urb, int status)
                          */
                         seg->status = WA_SEG_ABORTED;
                         seg->result = -ENOENT;
-                        spin_lock_irqsave(&rpipe->seg_lock, flags2);
                         list_del(&seg->list_node);
                         xfer->segs_done++;
-                        spin_unlock_irqrestore(&rpipe->seg_lock, flags2);
                         break;
                 case WA_SEG_DONE:
                 case WA_SEG_ERROR:
@@ -2026,6 +2029,7 @@ int wa_urb_dequeue(struct wahc *wa, struct urb *urb, int status)
                         break;
                 }
         }
+        spin_unlock(&rpipe->seg_lock);
         xfer->result = urb->status;     /* -ENOENT or -ECONNRESET */
         done = __wa_xfer_is_done(xfer);
         spin_unlock_irqrestore(&xfer->lock, flags);