Dmitry Vyukov wrote: > On Tue, Jun 5, 2018 at 3:45 PM, Tetsuo Handa > <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > > Dmitry, can you assign VM resources for a git tree for this bug? This bug wants to fight > > against https://github.com/google/syzkaller/blob/master/docs/syzbot.md#no-custom-patches ... > > Hi Tetsuo, > > Most of the reasons for not doing it still stand. A syzkaller instance > will produce not just this bug, it will produce hundreds of different > bugs. Then the question is: what to do with these bugs? Report all to > mailing lists? Is it possible to add linux-next.git tree as a target for fuzzing? If yes, we can try debug patches easily, in addition to find bugs earlier than now. > I think the solution here is just to run syzkaller instance locally. > It's just a program anybody can run it on any kernel with any custom > patches. Moreover for local instance it's also possible to limit set > of tested syscalls to increase probability of hitting this bug and at > the same time filter out most of other bugs. If this bug is reproducible with VM resources individual developer can afford... Since my Linux development environment is VMware guests on a Windows PC, I can't run VM instance which needs KVM acceleration. Also, due to security policy, I can't utilize external VM resources available on the Internet, as well as I can't use ssh and git protocols. Speak of this bug, even with a lot of VM instances, syzbot can reproduce this bug only once or twice per a day. Thus, the question for me boils down to, whether I can reproduce this bug using one VMware guest instance with 4GB of memory. Effectively, I don't have access to environments for running syzkaller instance... > > Do we have any idea about the guilty subsystem? You mentioned > bdi_unregister, why? What would be the set of syscalls to concentrate > on? > I will do a custom run when I get around to it, if nobody else beats me to it. Because bdi_unregister() does "bdi->dev = NULL;" which wb_workfn() is hitting NULL pointer dereference.
