binderfs interferes with syzkaller?

[Dmitry Vyukov]

Hi binder maintainers,

It seems that something has happened and now syzbot has 0 coverage in
drivers/android/binder.c:
https://storage.googleapis.com/syzkaller/cover/ci-upstream-kasan-gce-root.html
It covered at least something there before as it found some bugs in binder code.
I _suspect_ it may be related to introduction binderfs, but it's
purely based on the fact that binderfs changed lots of things there.
And I see it claims to be backward compatible.

syzkaller strategy to reach binder devices is to use
CONFIG_ANDROID_BINDER_DEVICES to create a bunch of binderN devices (to
give each test process a private one):
https://github.com/google/syzkaller/blob/master/dashboard/config/upstream-kasan.config#L5671

Then it knows how to open these /dev/binderN devices:
https://github.com/google/syzkaller/blob/master/sys/linux/dev_binder.txt#L22
and do stuff with them.

Did these devices disappear or something?