[PATCH bpf v2] bpf: btf: fix truncated last_member_type_id in btf_struct_resolve

From: Lorenz Bauer <oss@lmb.io>
To: Martin KaFai Lau <martin.lau@linux.dev>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>, Song Liu <song@kernel.org>,
	Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,
	Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
	Jiri Olsa <jolsa@kernel.org>
Cc: Lorenz Bauer <oss@lmb.io>,
	bpf@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH bpf v2] bpf: btf: fix truncated last_member_type_id in btf_struct_resolve
Date: Sat, 10 Sep 2022 11:01:20 +0000	[thread overview]
Message-ID: <20220910110120.339242-1-oss@lmb.io> (raw)

When trying to finish resolving a struct member, btf_struct_resolve
saves the member type id in a u16 temporary variable. This truncates
the 32 bit type id value if it exceeds UINT16_MAX.

As a result, structs that have members with type ids > UINT16_MAX and
which need resolution will fail with a message like this:

    [67414] STRUCT ff_device size=120 vlen=12
        effect_owners type_id=67434 bits_offset=960 Member exceeds struct_size

Fix this by changing the type of last_member_type_id to u32.

Fixes: a0791f0df7d2 ("bpf: fix BTF limits")
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Lorenz Bauer <oss@lmb.io>
---
 kernel/bpf/btf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 7e64447659f3..36fd4b509294 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3128,7 +3128,7 @@ static int btf_struct_resolve(struct btf_verifier_env *env,
 	if (v->next_member) {
 		const struct btf_type *last_member_type;
 		const struct btf_member *last_member;
-		u16 last_member_type_id;
+		u32 last_member_type_id;
 
 		last_member = btf_type_member(v->t) + v->next_member - 1;
 		last_member_type_id = last_member->type;
-- 
2.34.1

