Re: [PATCH bpf-next 0/2] bpf: Cancel special fields in resizable hashtab on recycle

On Tue Aug 11, 2026 at 11:55 AM CEST, chenyuan_fl wrote:
> From: Yuan Chen <[email protected]>
>
> The resizable hashtab (BPF_MAP_TYPE_RHASH) still eagerly calls
> bpf_obj_free_fields() when an element is deleted or its value is
> replaced, which runs kptr destructors in the caller's execution context.
> This is unsafe for BPF programs running in NMI context (e.g. perf_event
> programs attached to hardware PMU overflows), where referenced kptr
> destructors may take locks or otherwise cannot run.
>
> Commit a3a81d247651 ("bpf: Cancel special fields on map value recycle")
> switched the hash map and array recycle paths to bpf_obj_cancel_fields(),
> which only cancels NMI-safe fields (timer, workqueue, task_work), but it
> missed the resizable hashtab. Patch 1 applies the same semantics to
> rhtab; patch 2 adds a regression test.
>
> Yuan Chen (2):
>   bpf: Cancel special fields in resizable hashtab on recycle
>   selftests/bpf: Test rhtab kptr recycle from NMI context
>

At least go through the mailing list before sending patches.

https://lore.kernel.org/bpf/[email protected]

pw-bot: cr

>  kernel/bpf/hashtab.c                          |  28 +++--
>  .../selftests/bpf/prog_tests/rhtab_kptr.c     |  87 +++++++++++++++
>  .../testing/selftests/bpf/progs/rhtab_kptr.c  | 101 ++++++++++++++++++
>  3 files changed, 207 insertions(+), 9 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/rhtab_kptr.c
>  create mode 100644 tools/testing/selftests/bpf/progs/rhtab_kptr.c