Oops, I replied to the wrong email message -- sorry. This was intended to be about the problem with the yurex driver, not the iowarrior driver. Alan Stern On Tue, 20 Aug 2019, Alan Stern wrote: > On Mon, 19 Aug 2019, Oliver Neukum wrote: > > > Am Montag, den 19.08.2019, 07:48 -0700 schrieb syzbot: > > > Hello, > > > > > > syzbot found the following crash on: > > > > > > HEAD commit: d0847550 usb-fuzzer: main usb gadget fuzzer driver > > > git tree: https://github.com/google/kasan.git usb-fuzzer > > > console output: https://syzkaller.appspot.com/x/log.txt?x=139be302600000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=dbc9c80cc095da19 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=cfe6d93e0abab9a0de05 > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12fe6b02600000 > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1548189c600000 > > > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > > Reported-by: syzbot+cfe6d93e0abab9a0de05@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > > #syz test: https://github.com/google/kasan.git d0847550 > > There's no need for us to work at cross purposes on this. We can go > with your approach. > > However, the code is more complicated than your patch accounts for. > The wait can finish in several different ways: > > (1) The control URB succeeds and the interrupt URB gets an > acknowledgment. > > (2) The control URB completes with an error. > > (3) The wait times out. > > (4) A disconnect occurs. > > Your patch doesn't handle cases (1) and (3). (And it doesn't get rid > of the dev->waitq field, which is no longer used.) > > In fact, (1) is a little ambiguous. When the interrupt URB gets a > command acknowledgment, there's no way (as far as I can tell) to know > which command was acknowledged -- particularly if a prior command URB > had to be cancelled because it timed out. > > And as it turns out, the driver neglects to kill the command URB in > case (3). Furthermore, the driver doesn't have mutual exclusion for > writes. So there's nothing to prevent the command URB from being > submitted while it is still active (syzbot's new crash). > > I have to wonder if anybody's actually using this driver. It seems to > be pretty broken. Maybe we should just mark it as such and forget > about fixing it. > > Alan Stern
