linux-kernel - [PATCH 4.18 091/135] bpf: btf: Fix end boundary calculation for type section

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Date:   Tue, 16 Oct 2018 19:05:21 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
        Martin KaFai Lau <kafai@...com>, Yonghong Song <yhs@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.18 091/135] bpf: btf: Fix end boundary calculation for type section

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Martin KaFai Lau <kafai@...com>

[ Upstream commit 4b1c5d917d34f705096bb7dd8a2bd19b0881970e ]

The end boundary math for type section is incorrect in
btf_check_all_metas().  It just happens that hdr->type_off
is always 0 for now because there are only two sections
(type and string) and string section must be at the end (ensured
in btf_parse_str_sec).

However, type_off may not be 0 if a new section would be added later.
This patch fixes it.

Fixes: f80442a4cd18 ("bpf: btf: Change how section is supported in btf_header")
Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Signed-off-by: Martin KaFai Lau <kafai@...com>
Acked-by: Yonghong Song <yhs@...com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/bpf/btf.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -1844,7 +1844,7 @@ static int btf_check_all_metas(struct bt
 
 	hdr = &btf->hdr;
 	cur = btf->nohdr_data + hdr->type_off;
-	end = btf->nohdr_data + hdr->type_len;
+	end = cur + hdr->type_len;
 
 	env->log_type_id = 1;
 	while (cur < end) {