On Mon, Jul 29, 2024 at 4:23 AM andrey.konovalov@linux.dev wrote:
From: Andrey Konovalov andreyknvl@gmail.com
Commit a7f3813e589f ("usb: gadget: dummy_hcd: Switch to hrtimer transfer scheduler") switched dummy_hcd to use hrtimer and made the timer's callback be executed in the hardirq context.
With that change, __usb_hcd_giveback_urb now gets executed in the hardirq context, which causes problems for KCOV and KMSAN.
One problem is that KCOV now is unable to collect coverage from the USB code that gets executed from the dummy_hcd's timer callback, as KCOV cannot collect coverage in the hardirq context.
Another problem is that the dummy_hcd hrtimer might get triggered in the middle of a softirq with KCOV remote coverage collection enabled, and that causes a WARNING in KCOV, as reported by syzbot. (I sent a separate patch to shut down this WARNING, but that doesn't fix the other two issues.)
Finally, KMSAN appears to ignore tracking memory copying operations that happen in the hardirq context, which causes false positive kernel-infoleaks, as reported by syzbot.
Hi Andrey,
FWIW this problem is tracked as https://github.com/google/kmsan/issues/92, I'll try to revisit it in September.