Patch "usb: chipidea: udc: fix NULL ptr dereference in isr_setup_status_phase" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

usb: chipidea: udc: fix NULL ptr dereference in isr_setup_status_phase

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
usb-chipidea-udc-fix-null-ptr-dereference-in-isr_setup_status_phase.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Clemens Gruber <[email protected]>
Date: Mon, 5 Sep 2016 19:29:58 +0200
Subject: usb: chipidea: udc: fix NULL ptr dereference in isr_setup_status_phase

From: Clemens Gruber <[email protected]>

commit 6f3c4fb6d05e63c9c6d8968302491c3a5457be61 upstream.

Problems with the signal integrity of the high speed USB data lines or noise on reference ground lines can cause the i.MX6 USB controller to violate USB specs and exhibit unexpected behavior.

It was observed that USBi_UI interrupts were triggered first and when isr_setup_status_phase was called, ci->status was NULL, which lead to a NULL pointer dereference kernel panic.

This patch fixes the kernel panic, emits a warning once and returns -EPIPE to halt the device and let the host get stalled.
It also adds a comment to point people, who are experiencing this issue, to their USB hardware design.

---
 drivers/usb/chipidea/udc.c |    9 +++++++++
 1 file changed, 9 insertions(+)

@@ -939,6 +939,15 @@ static int isr_setup_status_phase(struct
 	int retval;
 	struct ci_hw_ep *hwep;
 
+	/*
+	 * Unexpected USB controller behavior, caused by bad signal integrity
+	 * or ground reference problems, can lead to isr_setup_status_phase
+	 * being called with ci->status equal to NULL.
+	 * If this situation occurs, you should review your USB hardware design.
+	 */
+	if (WARN_ON_ONCE(!ci->status))
+		return -EPIPE;
+
 	hwep = (ci->ep0_dir == TX) ? ci->ep0out : ci->ep0in;
 	ci->status->context = ci;
 	ci->status->complete = isr_setup_status_complete;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/usb-chipidea-udc-fix-null-ptr-dereference-in-isr_setup_status_phase.patch