On Thu, Dec 5, 2019 at 11:22 AM Paolo Bonzini [off-list ref] wrote:

On 05/12/19 11:16, Dmitry Vyukov wrote:

quoted

On Thu, Dec 5, 2019 at 11:13 AM Paolo Bonzini [off-list ref] wrote:

quoted

On 04/12/19 22:41, syzbot wrote:

quoted

syzbot has bisected this bug to:

commit 2de50e9674fc4ca3c6174b04477f69eb26b4ee31
Author: Russell Currey [off-list ref]
Date:   Mon Feb 8 04:08:20 2016 +0000

    powerpc/powernv: Remove support for p5ioc2

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=127a042ae00000
start commit:   76bb8b05 Merge tag 'kbuild-v5.5' of
git://git.kernel.org/p..
git tree:       upstream
final crash:    https://syzkaller.appspot.com/x/report.txt?x=117a042ae00000
console output: https://syzkaller.appspot.com/x/log.txt?x=167a042ae00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b
dashboard link:
https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000

Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com
Fixes: 2de50e9674fc ("powerpc/powernv: Remove support for p5ioc2")

For information about bisection process see:
https://goo.gl/tpsmEJ#bisection

Why is everybody being CC'd, even if the bug has nothing to do with the
person's subsystem?

The To list should be intersection of 2 groups of emails: result of
get_maintainers.pl on the file identified as culprit in the crash
message + emails extracted from the bisected to commit.

Ah, and because the machine is a KVM guest, kvm_wait appears in a lot of
backtrace and I get to share syzkaller's joy every time. :)

I don't see any mention of "kvm" in the crash report. And it's only 1
file, not all of them, in this case I would expect it to be
drivers/video/fbdev/core/fbcon.c. So it should be something different.

This bisect result is bogus, though Tetsuo found the bug anyway.
Perhaps you can exclude commits that only touch architectures other than
x86?

We do this. It work sometimes. But sometimes it hits non-deterministic
kernel build bugs:
https://github.com/google/syzkaller/issues/1271#issuecomment-559093018
And in this case it hit some git bisect weirdness which I can't explain yet:
https://github.com/google/syzkaller/issues/1527