On Tue, 20 Aug 2019, Oliver Neukum wrote: > Am Dienstag, den 20.08.2019, 10:18 -0400 schrieb Alan Stern: > > 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+cfe6d93e0abab9a0d...@syzkaller.appspotmail.com > > > > > > > > > > #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. > > I absolutely agree. There is something quite wrong in this driver. > Unfortunately this is likely exploitable by a malicious gadget, > so just ignoring this is a bad option. I will need to go through the > logic. Or do you want to have a shot at it? > > The patch was really only for testing. I wanted to know whether > I was hitting this very issue. This driver will need more surgery.
If you would like to work on it, that's fine with me. Alan Stern