As reported by Kumar in [0], the shared ownership implementation for BPF programs has some race conditions which need to be addressed before it can safely be used. This patch does so in a minimal way instead of ripping out shared ownership entirely, as proper fixes for the issues raised will follow ASAP, at which point this patch's commit can be reverted to re-enable shared ownership. The patch removes the ability to call bpf_refcount_acquire_impl from BPF programs. Programs can only bump refcount and obtain a new owning reference using this kfunc, so removing the ability to call it effectively disables shared ownership. Instead of changing success / failure expectations for bpf_refcount-related selftests, this patch just disables them from running for now. [0]: https://lore.kernel.org/bpf/d7hyspcow5wtjcmw4fugdgyp3fwhljwuscp3xyut5qnwivyeru@ysdq543otzv2/ Reported-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx> --- kernel/bpf/verifier.c | 5 ++++- tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c | 2 -- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 0d73139ee4d8..5c4aa393f65a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10509,7 +10509,10 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ verbose(env, "arg#%d doesn't point to a type with bpf_refcount field\n", i); return -EINVAL; } - + if (rec->refcount_off >= 0) { + verbose(env, "bpf_refcount_acquire calls are disabled for now\n"); + return -EINVAL; + } meta->arg_refcount_acquire.btf = reg->btf; meta->arg_refcount_acquire.btf_id = reg->btf_id; break; diff --git a/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c b/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c index 2ab23832062d..595cbf92bff5 100644 --- a/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c +++ b/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c @@ -9,10 +9,8 @@ void test_refcounted_kptr(void) { - RUN_TESTS(refcounted_kptr); } void test_refcounted_kptr_fail(void) { - RUN_TESTS(refcounted_kptr_fail); } -- 2.34.1
