Re: [PATCH bpf-next 0/2] bpf: Track overlapping RCU protection

On Thu Aug 6, 2026 at 1:39 AM CEST, Ning Ding wrote:
> Preemption-disabled and IRQ-disabled regions provide RCU protection, but
> the verifier does not account for them. Current implementation can invalidate
> a task kptr while another RCU source remains active, or keep it valid
> after the final source ends.
>
> Track these regions and invalidate RCU-protected pointers only after the
> last protection ends. Add task kptr tests for overlapping protection and
> final-exit rejection.
>
> This follows review of the applied spin-unlock fix series [1].
>
> Tested in QEMU/KVM:
>   ./test_progs -t task_kfunc
>   ./test_progs -t preempt_lock
>   ./test_progs -t irq
>

Overall, looks good. There are various failures in CI, so you might need to
update or adjust existing selftests.

Make sure to include selftest changes for _existing_ tests within the kernel
commit making changes, so as to preserve bisection. Your extra tests should
still go in a separate commit.

Also, do we need that was_in_rcu_cs logic for bpf_spin_lock(). Would it be
possible to drop it and do it the same way you've done it for other cases?
If that makes sense, I would fold that cleanup in the first patch as well.

https://patchwork.kernel.org/project/netdevbpf/patch/[email protected]

pw-bot: cr

> [1] https://lore.kernel.org/r/[email protected]
>
> Ning Ding (2):
>   bpf: Account for preempt and IRQ state in RCU protection
>   selftests/bpf: Test overlapping RCU protection
>
>  kernel/bpf/verifier.c                         |  13 +-
>  .../selftests/bpf/prog_tests/task_kfunc.c     |   6 +
>  .../selftests/bpf/progs/task_kfunc_common.h   |   2 +
>  .../selftests/bpf/progs/task_kfunc_failure.c  |  49 ++++++
>  .../selftests/bpf/progs/task_kfunc_success.c  | 147 ++++++++++++++++++
>  5 files changed, 214 insertions(+), 3 deletions(-)
>
>
> base-commit: 11c1e836710dcba03e50454a4eedfdbaf8d3050e