Re: Binder regression caused by commit a43cfc87caaf

[Liam Howlett]

* Ondrej Mosnacek <omosnace@xxxxxxxxxx> [220808 06:13]:
> Hello,
> 
> FYI, since commit a43cfc87caaf ("android: binder: stop saving a
> pointer to the VMA") (found by git bisect) the binder test in
> selinux-testsuite [1] started to trigger a lockdep assert BUG() in
> find_vma() - see the end of [2] for an example.
> 
> A minimal reproducer is:
> ```
> git clone https://github.com/SELinuxProject/selinux-testsuite.git
> cd selinux-testsuite/tests/binder
> make
> setenforce 0  # if SELinux is enabled
> ./init_binder.sh || true
> ./manager -n -v & sleep 2
> ./service_provider -n -v
> ```
> Requires the equivalent of libselinux-devel, make, gcc, and git-core
> Fedora packages.
> The last command will trigger the BUG; on good kernels it will
> successfully enter the ioctl loop.
> 
> [1] https://github.com/SELinuxProject/selinux-testsuite/
> [2] https://s3.us-east-1.amazonaws.com/arr-cki-prod-datawarehouse-public/datawarehouse-public/2022/08/07/redhat:606549366/build_x86_64_redhat:606549366_x86_64/tests/5/results_0001/console.log/console.log
> 

Thanks.  It looks like binder has some paths that are not taking the
necessary mmap lock for using VMAs.  I'm looking into it now.

Regards,
Liam