[PATCH v1 2/2] usb: dwc3: Prevent cleanup cancelled requests at the same time.

[Daehwan Jung]

We added cleanup cancelled requests when ep cmd timeout on ep dequeue
because there's no complete interrupt then. But, we find out new case
that complete interrupt comes up later. list_for_each_entry_safe is
used when cleanup cancelled requests and it has vulnerabilty on multi-core
environment. dwc3_gadget_giveback unlocks dwc->lock temporarily and other
core(ISR) can get lock and try to cleanup them again. It could cause
list_del corruption and we use DWC3_EP_END_TRANSFER_PENDING to prevent it.

1. MTP server cancels -> ep dequeue -> ep cmd timeout(END_TRANSFER)
   -> cleanup cancelled requests -> dwc3_gadget_giveback -> list_del -> release lock temporarily
2. Complete with END_TRANSFER -> ISR(dwc3_gadget_endpoint_command_complete) gets lock
   -> cleanup cancelled requests -> dwc3_gadget_giveback -> list_del
3. MTP server process gets lock again -> tries to access POISON list(list_del corruption)

[  205.014697] [2:      MtpServer: 5032] dwc3 10b00000.dwc3: request cancelled with wrong reason:5
[  205.014719] [2:      MtpServer: 5032] list_del corruption, ffffff88b6963968->next is LIST_POISON1 (dead000000000100)

Change-Id: I9df055c6c04855edd09e330300914454a6657a23
Signed-off-by: Daehwan Jung <dh10.jung@xxxxxxxxxxx>

Change-Id: If87c88c3bb4c17ea1a5bde2bfec1382769f7ecab
Signed-off-by: Daehwan Jung <dh10.jung@xxxxxxxxxxx>
---
 drivers/usb/dwc3/gadget.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 3ad3bc5813ca..2e0183512d5b 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2046,8 +2046,11 @@ static int dwc3_gadget_ep_dequeue(struct usb_ep *ep,
 
 			/* If ep cmd fails, then force to giveback cancelled requests here */
 			if (!(dep->flags & DWC3_EP_END_TRANSFER_PENDING)) {
-				dep->flags &= ~DWC3_EP_TRANSFER_STARTED;
+				dep->flags |= DWC3_EP_END_TRANSFER_PENDING;
 				dwc3_gadget_ep_cleanup_cancelled_requests(dep);
+
+				dep->flags &= ~DWC3_EP_TRANSFER_STARTED;
+				dep->flags &= ~DWC3_EP_END_TRANSFER_PENDING;
 			}
 
 			dep->flags &= ~DWC3_EP_WAIT_TRANSFER_COMPLETE;
@@ -3426,9 +3429,12 @@ static void dwc3_gadget_endpoint_command_complete(struct dwc3_ep *dep,
 	if (dep->stream_capable)
 		dep->flags |= DWC3_EP_IGNORE_NEXT_NOSTREAM;
 
+	if (!(dep->flags & DWC3_EP_END_TRANSFER_PENDING)) {
+		dwc3_gadget_ep_cleanup_cancelled_requests(dep);
+	}
+
 	dep->flags &= ~DWC3_EP_END_TRANSFER_PENDING;
 	dep->flags &= ~DWC3_EP_TRANSFER_STARTED;
-	dwc3_gadget_ep_cleanup_cancelled_requests(dep);
 
 	if (dep->flags & DWC3_EP_PENDING_CLEAR_STALL) {
 		struct dwc3 *dwc = dep->dwc;
-- 
2.31.1