From 5b481acab4ce017fda8166fa9428511da41109e5 Mon Sep 17 00:00:00 2001 From: Benjamin Tissoires Date: Tue, 6 Dec 2022 15:59:32 +0100 Subject: bpf: do not rely on ALLOW_ERROR_INJECTION for fmod_ret The current way of expressing that a non-bpf kernel component is willing to accept that bpf programs can be attached to it and that they can change the return value is to abuse ALLOW_ERROR_INJECTION. This is debated in the link below, and the result is that it is not a reasonable thing to do. Reuse the kfunc declaration structure to also tag the kernel functions we want to be fmodret. This way we can control from any subsystem which functions are being modified by bpf without touching the verifier. Link: https://lore.kernel.org/all/20221121104403.1545f9b5@gandalf.local.home/ Suggested-by: Alexei Starovoitov Signed-off-by: Benjamin Tissoires Acked-by: Alexei Starovoitov Link: https://lore.kernel.org/r/20221206145936.922196-2-benjamin.tissoires@redhat.com --- net/bpf/test_run.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'net/bpf') diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 13d578ce2a09..5079fb089b5f 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -489,7 +489,6 @@ int noinline bpf_fentry_test1(int a) return a + 1; } EXPORT_SYMBOL_GPL(bpf_fentry_test1); -ALLOW_ERROR_INJECTION(bpf_fentry_test1, ERRNO); int noinline bpf_fentry_test2(int a, u64 b) { @@ -733,7 +732,15 @@ noinline void bpf_kfunc_call_test_destructive(void) __diag_pop(); -ALLOW_ERROR_INJECTION(bpf_modify_return_test, ERRNO); +BTF_SET8_START(bpf_test_modify_return_ids) +BTF_ID_FLAGS(func, bpf_modify_return_test) +BTF_ID_FLAGS(func, bpf_fentry_test1, KF_SLEEPABLE) +BTF_SET8_END(bpf_test_modify_return_ids) + +static const struct btf_kfunc_id_set bpf_test_modify_return_set = { + .owner = THIS_MODULE, + .set = &bpf_test_modify_return_ids, +}; BTF_SET8_START(test_sk_check_kfunc_ids) BTF_ID_FLAGS(func, bpf_kfunc_call_test1) @@ -1668,7 +1675,8 @@ static int __init bpf_prog_test_run_init(void) }; int ret; - ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_prog_test_kfunc_set); + ret = register_btf_fmodret_id_set(&bpf_test_modify_return_set); + ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_prog_test_kfunc_set); ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_prog_test_kfunc_set); ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_prog_test_kfunc_set); return ret ?: register_btf_id_dtor_kfuncs(bpf_prog_test_dtor_kfunc, -- cgit v1.2.3