linux-kernel - [PATCH] usb: cdnsp: Fix issue with detecting command completion event

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID:
 <PH7PR07MB953855E1D951721A143A83ADDD88A@PH7PR07MB9538.namprd07.prod.outlook.com>
Date: Wed, 7 May 2025 07:22:40 +0000
From: Pawel Laszczak <pawell@...ence.com>
To: "peter.chen@...nel.org" <peter.chen@...nel.org>
CC: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Pawel Laszczak
	<pawell@...ence.com>
Subject: [PATCH] usb: cdnsp: Fix issue with detecting command completion event

In some cases, there is a small-time gap in which CMD_RING_BUSY
can be cleared by controller but adding command completion event
to event ring will be delayed. As the result driver will return
error code.
This behavior has been detected on usbtest driver (test 9) with
configuration including ep1in/ep1out bulk and ep2in/ep2out isoc
endpoint.
Probably this gap occurred because controller was busy with adding
some other events to event ring.
The CMD_RING_BUSY is cleared to '0' when the Command Descriptor
has been executed and not when command completion event has been
added to event ring.

To fix this issue for this test the small delay is sufficient
less than 10us) but to make sure the problem doesn't happen again
in the future the patch introduce 3 retries to check with delay
about 100us before returning error code

Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
cc: stable@...r.kernel.org
Signed-off-by: Pawel Laszczak <pawell@...ence.com>
---
 drivers/usb/cdns3/cdnsp-gadget.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/cdns3/cdnsp-gadget.c b/drivers/usb/cdns3/cdnsp-gadget.c
index f773518185c9..0eb11b5dd9d3 100644
--- a/drivers/usb/cdns3/cdnsp-gadget.c
+++ b/drivers/usb/cdns3/cdnsp-gadget.c
@@ -547,6 +547,7 @@ int cdnsp_wait_for_cmd_compl(struct cdnsp_device *pdev)
 	dma_addr_t cmd_deq_dma;
 	union cdnsp_trb *event;
 	u32 cycle_state;
+	u32 retry = 3;
 	int ret, val;
 	u64 cmd_dma;
 	u32  flags;
@@ -578,8 +579,23 @@ int cdnsp_wait_for_cmd_compl(struct cdnsp_device *pdev)
 		flags = le32_to_cpu(event->event_cmd.flags);
 
 		/* Check the owner of the TRB. */
-		if ((flags & TRB_CYCLE) != cycle_state)
+		if ((flags & TRB_CYCLE) != cycle_state) {
+			/*
+			 *Give some extra time to get chance controller
+			 * to finish command before returning error code.
+			 * Checking CMD_RING_BUSY is not sufficient because
+			 * this bit is cleared to '0' when the Command
+			 * Descriptor has been executed by controller
+			 * and not when command completion event has
+			 * be added to event ring.
+			 */
+			if (retry--) {
+				usleep_range(90, 100);
+				continue;
+			}
+
 			return -EINVAL;
+		}
 
 		cmd_dma = le64_to_cpu(event->event_cmd.cmd_trb);
 
-- 
2.43.0