[PATCH v2 1/2] bpf/btf: Fix is_int_ptr()

From: Feng zhou
Date: Fri Apr 07 2023 - 04:47:35 EST


From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>

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 don't 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@xxxxxxxxxxxxx>
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Signed-off-by: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
---
kernel/bpf/btf.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 593c45a294d0..17c65de1e48b 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5913,9 +5913,8 @@ 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);
}
--
2.20.1