From: Andrii Nakryiko Date: Fri, 19 Jul 2019 19:46:03 +0000 (-0700) Subject: libbpf: sanitize VAR to conservative 1-byte INT X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=1d4126c4e119;p=openwrt%2Fstaging%2Fblogic.git libbpf: sanitize VAR to conservative 1-byte INT If VAR in non-sanitized BTF was size less than 4, converting such VAR into an INT with size=4 will cause BTF validation failure due to violationg of STRUCT (into which DATASEC was converted) member size. Fix by conservatively using size=1. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov --- diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 87168f21ef43..d8833ff6c4a1 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -1377,8 +1377,13 @@ static void bpf_object__sanitize_btf(struct bpf_object *obj) if (!has_datasec && kind == BTF_KIND_VAR) { /* replace VAR with INT */ t->info = BTF_INFO_ENC(BTF_KIND_INT, 0, 0); - t->size = sizeof(int); - *(int *)(t+1) = BTF_INT_ENC(0, 0, 32); + /* + * using size = 1 is the safest choice, 4 will be too + * big and cause kernel BTF validation failure if + * original variable took less than 4 bytes + */ + t->size = 1; + *(int *)(t+1) = BTF_INT_ENC(0, 0, 8); } else if (!has_datasec && kind == BTF_KIND_DATASEC) { /* replace DATASEC with STRUCT */ struct btf_var_secinfo *v = (void *)(t + 1);