On 2026/8/5 23:33, Kaitao Cheng wrote: > The verifier currently has a hard-coded allowlist of kfuncs that may be > called while a BPF program holds a bpf_spin_lock. This works for the > small set of built-in kfuncs known to the verifier, but it does not give > kfunc providers a registration-time way to declare that a kfunc is safe > in such a region. In particular, module kfuncs cannot be added to that > allowlist without changing verifier code. > > This series adds a new KF_SPINLOCK_SAFE kfunc flag and teaches the > verifier to use kfunc registration metadata when deciding whether a > kfunc call is allowed while a bpf_spin_lock is held. > > The built-in kfuncs that are currently accepted by the verifier's > lock-held allowlist are annotated with the new flag. This preserves the > existing behavior while removing the verifier-side category checks and > uses the same mechanism for built-in and module kfuncs. > > The selftest coverage marks one bpf_testmod kfunc as KF_SPINLOCK_SAFE > and verifies that it can be called under a bpf_spin_lock. It also calls > another registered but unmarked bpf_testmod kfunc under the lock and > checks that the verifier rejects it. > > Changes in v2: > - Rename KF_SPIN_LOCK to KF_SPINLOCK_SAFE. (Kumar Kartikeya Dwivedi, > Leon Hwang) > - Deprecate the verifier's lock-held allowlist mechanism and annotate the > relevant kfuncs uniformly with KF_SPINLOCK_SAFE (Kumar Kartikeya Dwivedi) > - Add selftests. (Leon Hwang) > > Link to v1: > https://lore.kernel.org/bpf/[email protected]/ > > Kaitao Cheng (3): > bpf: Add KF_SPINLOCK_SAFE flag for kfuncs under bpf_spin_lock > bpf: Mark existing lock-safe kfuncs with KF_SPINLOCK_SAFE > selftests/bpf: Test module kfunc calls under spin lock > > include/linux/btf.h | 1 + > kernel/bpf/arena.c | 6 +- > kernel/bpf/helpers.c | 56 ++++++++++--------- > kernel/bpf/rqspinlock.c | 8 +-- > kernel/bpf/verifier.c | 38 +++---------- > .../selftests/bpf/prog_tests/kfunc_call.c | 2 + > .../selftests/bpf/progs/kfunc_call_fail.c | 12 ++++ > .../selftests/bpf/progs/kfunc_call_test.c | 12 ++++ > .../selftests/bpf/test_kmods/bpf_testmod.c | 2 +- > 9 files changed, 72 insertions(+), 65 deletions(-) >
Nice to drop those 'is_*_kfunc()' helpers in verifier. BTW, some of those kfuncs can be dropped from the special_kfunc_list. That would be better. Any way, this series looks good to me. Acked-by: Leon Hwang <[email protected]>
