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authorYonghong Song <yhs@fb.com>2020-05-13 22:32:05 -0700
committerAlexei Starovoitov <ast@kernel.org>2020-05-14 12:50:10 -0700
commite92888c72fbdc6f9d07b3b0604c012e81d7c0da7 (patch)
treeb2ad05c336d5bb8cf8cbbc5081f8848338516263
parent625236ba3832ae947cb3ebb7acc1f30788b274ef (diff)
downloadlinux-e92888c72fbdc6f9d07b3b0604c012e81d7c0da7.tar.gz
bpf: Enforce returning 0 for fentry/fexit progs
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@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/20200514053206.1298415-1-yhs@fb.com
-rw-r--r--kernel/bpf/verifier.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index fa1d8245b925..a44ba6672688 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7059,6 +7059,23 @@ 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) {
+ 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;
}