On 5/13/20 11:14 PM, Andrii Nakryiko wrote:
On Wed, May 13, 2020 at 10:32 PM Yonghong Song <yhs@xxxxxx> wrote:Currently, tracing/fentry and tracing/fexit prog return values are not enforced. In trampoline codes, the fentry/fexit prog return values are ignored. Let us enforce it to be 0 to avoid confusion and allows potential future extension. This patch also explicitly added return value checking for tracing/raw_tp, tracing/fmod_ret, and freplace programs such that these program return values can be anything. The purpose are two folds: 1. to make it explicit about return value expectations for these programs in verifier. 2. for tracing prog_type, if a future attach type is added, the default is -ENOTSUPP which will enforce to specify return value ranges explicitly. Fixes: fec56f5890d9 ("bpf: Introduce BPF trampoline") Signed-off-by: Yonghong Song <yhs@xxxxxx> ---Looks good, except a nit below. Acked-by: Andrii Nakryiko <andriin@xxxxxx> [...]diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index fa1d8245b925..2d80cce0a28a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7059,6 +7059,24 @@ static int check_return_code(struct bpf_verifier_env *env) return 0; range = tnum_const(0); break; + case BPF_PROG_TYPE_TRACING: + switch ((env->prog->expected_attach_type)) {nit: extra pair of ()?
Sorry about this. Not sure whether it is worthwhile to send another revision. Please let me know if another revision is needed.
+ case BPF_TRACE_FENTRY: + case BPF_TRACE_FEXIT: + range = tnum_const(0); + break; + case BPF_TRACE_RAW_TP: + case BPF_MODIFY_RETURN: + return 0; + default: + return -ENOTSUPP; + } + + break; + case BPF_PROG_TYPE_EXT: + /* freplace program can return anything as its return value + * depends on the to-be-replaced kernel func or bpf program. + */ default: return 0; } -- 2.24.1
