linux-kernel - [PATCH v3 1/2] bpf/btf: Fix is_int

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Date:   Mon, 10 Apr 2023 16:59:07 +0800
From:   Feng zhou <zhoufeng.zf@...edance.com>
To:     martin.lau@...ux.dev, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        mykolal@...com, shuah@...nel.org
Cc:     bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, linux-kselftest@...r.kernel.org,
        yangzhenze@...edance.com, wangdongdong.6@...edance.com,
        zhouchengming@...edance.com, zhoufeng.zf@...edance.com
Subject: [PATCH v3 1/2] bpf/btf: Fix is_int_ptr()

From: Feng Zhou <zhoufeng.zf@...edance.com>

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@...edance.com>
Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
Signed-off-by: Feng Zhou <zhoufeng.zf@...edance.com>
---
 kernel/bpf/btf.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 593c45a294d0..5abd8dfa6b70 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5910,12 +5910,8 @@ 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);
 }
-- 
2.20.1