linux-kernel - Re: general protection fault in syscall_return

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Date:   Sun, 08 Mar 2020 19:26:22 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>
Subject: Re: general protection fault in syscall_return_slowpath

Andy Lutomirski <luto@...nel.org> writes:
> On Sat, Mar 7, 2020 at 11:45 PM syzbot
> <syzbot+cd66e43794b178bb5cd6@...kaller.appspotmail.com> wrote:
> $ make -j4
> tools/syz-env/env.go:14:2: cannot find package
> "github.com/google/syzkaller/pkg/osutil" in any of:
>
> I'm sure that if I actually understood Go's delightful packaging
> system, I could reverse engineer your build system and figure out how
> to make it work.  But perhaps you could document the build process?
> Or maybe make 'make' just work?
>
> For kicks, I tried this:
>
> $ mkdir -p src/github.com/google
> $ ln -sr . src/github.com/google/syzkaller
> $ GOPATH=`/bin/pwd` make
> GOOS=linux GOARCH=amd64 go install ./syz-manager
> go install: no install location for directory
> /home/luto/apps/syzkaller/syz-manager outside GOPATH
>
> Are there instructions for just building syzkaller?  I don't want to
> install it, I don't want to fuzz my kernel -- I just want to run your
> reproducer.

https://github.com/google/syzkaller/blob/master/docs/executing_syzkaller_programs.md

That's how I build the binaries:

  mkdir foo
  export GOPATH=$HOME/foo

  cd foo
  go get -u -d github.com/google/syzkaller/...
  cd src/github.com/google/syzkaller
  make
  cp bin/linux_amd64/syz-execprog bin/linux_amd64/syz-executor $GOPATH

Of course you can build it somewhere and scp the executables to a test box.

And then to run it

  cd $GOPATH
  wget -O repro.syz https://syzkaller.appspot.com/x/repro.syz?x=12a42329e00000
  ./syz-execprog -procs 6 -repeat 0 -collide -disable none repro.syz

The command line options are a bit tedious as you have to look them up
in the comment in repro.syz.

A scripts which converts that comment into command line options or
syz-execprog simply taking it from repro.syz would indeed be handy.

A kernel with the config provided in the report and running that
reproducer is still not reproducing with a runtime of 8hrs+ :(

Thanks,

        tglx