patch "usb: chipidea: udc: fix NULL ptr dereference in" added to usb-linus

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

usb: chipidea: udc: fix NULL ptr dereference in

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

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

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(+)

index dfec5a176315..b93356834bb5 100644
@@ -949,6 +949,15 @@ static int isr_setup_status_phase(struct ci_hdrc *ci)
 	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;

2.9.3