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.
Change the hrtimer in dummy_hcd to execute the callback in the softirq context.
Reported-by: syzbot+2388cdaeb6b10f0c13ac@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=2388cdaeb6b10f0c13ac Reported-by: syzbot+17ca2339e34a1d863aad@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=17ca2339e34a1d863aad Fixes: a7f3813e589f ("usb: gadget: dummy_hcd: Switch to hrtimer transfer scheduler") Cc: stable@vger.kernel.org Signed-off-by: Andrey Konovalov andreyknvl@gmail.com
Hi Greg,
Could you pick up either this or Marcello's patch (https://lkml.org/lkml/2024/6/26/969)? In case they got lost.
Thank you!