On Tue, May 21, 2024 at 6:35 AM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > > On Mon, 20 May 2024 at 22:59, <andrey.konovalov@xxxxxxxxx> wrote: > > > > From: Andrey Konovalov <andreyknvl@xxxxxxxxx> > > > > After commit 8fea0c8fda30 ("usb: core: hcd: Convert from tasklet to BH > > workqueue"), usb_giveback_urb_bh() runs in the BH workqueue with > > interrupts enabled. > > > > Thus, the remote coverage collection section in usb_giveback_urb_bh()-> > > __usb_hcd_giveback_urb() might be interrupted, and the interrupt handler > > might invoke __usb_hcd_giveback_urb() again. > > > > This breaks KCOV, as it does not support nested remote coverage collection > > sections within the same context (neither in task nor in softirq). > > > > Update kcov_remote_start/stop_usb_softirq() to disable interrupts for the > > duration of the coverage collection section to avoid nested sections in > > the softirq context (in addition to such in the task context, which are > > already handled). > > Besides the issue pointed by the test robot: > > Acked-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > > Thanks for fixing this. Thanks for the ack! > This section of code does not rely on reentrancy, right? E.g. one > callback won't wait for completion of another callback? I think all should be good. Before the BH workqueue change, the code ran with interrupts disabled. > At some point we started seeing lots of "remote cover enable write > trace failed (errno 17)" errors while running syzkaller. Can these > errors be caused by this issue? This looks like a different issue. I also noticed this when I tried running a log with a bunch of USB programs via syz-execprog. Not sure why this happens, but I still see it with this patch applied. Thanks!