bpf/btf: Fix is_int_ptr()

When tracing a kernel function with arg type is u32*, btf_ctx_access()
would report error: arg2 type INT is not a struct.

The commit bb6728d75611 ("bpf: Allow access to int pointer arguments
in tracing programs") added support for int pointer, but did not skip
modifiers before checking it's type. This patch fixes it.

Fixes: bb6728d75611 ("bpf: Allow access to int pointer arguments in tracing programs")
Co-developed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20230410085908.98493-2-zhoufeng.zf@bytedance.com

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index ffc31a1..913b9d7 100644 (file)
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5921,12 +5921,8 @@ struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog)
 
 static bool is_int_ptr(struct btf *btf, const struct btf_type *t)
 {
-       /* t comes in already as a pointer */
-       t = btf_type_by_id(btf, t->type);
-
-       /* allow const */
-       if (BTF_INFO_KIND(t->info) == BTF_KIND_CONST)
-               t = btf_type_by_id(btf, t->type);
+       /* skip modifiers */
+       t = btf_type_skip_modifiers(btf, t->type, NULL);
 
        return btf_type_is_int(t);
 }