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 <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 87168f21ef43fdf3c0ebcca7e6250d6a44cc6f11..d8833ff6c4a13fb5711a19d60acbf31ac2ea36aa 100644 (file)
--- 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);