linux-kernel - [PATCH 5.15 504/917] libbpf: Fix BTF header parsing checks

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Message-Id: <20211115165445.854109371@linuxfoundation.org>
Date:   Mon, 15 Nov 2021 17:59:59 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Evgeny Vereshchagin <evvers@...ru>,
        Andrii Nakryiko <andrii@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 504/917] libbpf: Fix BTF header parsing checks

From: Andrii Nakryiko <andrii@...nel.org>

[ Upstream commit c825f5fee19caf301d9821cd79abaa734322de26 ]

Original code assumed fixed and correct BTF header length. That's not
always the case, though, so fix this bug with a proper additional check.
And use actual header length instead of sizeof(struct btf_header) in
sanity checks.

Fixes: 8a138aed4a80 ("bpf: btf: Add BTF support to libbpf")
Reported-by: Evgeny Vereshchagin <evvers@...ru>
Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Link: https://lore.kernel.org/bpf/20211023003157.726961-2-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/lib/bpf/btf.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index cfd701debcf61..1b9341ef638b0 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -231,13 +231,19 @@ static int btf_parse_hdr(struct btf *btf)
 		}
 		btf_bswap_hdr(hdr);
 	} else if (hdr->magic != BTF_MAGIC) {
-		pr_debug("Invalid BTF magic:%x\n", hdr->magic);
+		pr_debug("Invalid BTF magic: %x\n", hdr->magic);
 		return -EINVAL;
 	}
 
-	meta_left = btf->raw_size - sizeof(*hdr);
+	if (btf->raw_size < hdr->hdr_len) {
+		pr_debug("BTF header len %u larger than data size %u\n",
+			 hdr->hdr_len, btf->raw_size);
+		return -EINVAL;
+	}
+
+	meta_left = btf->raw_size - hdr->hdr_len;
 	if (meta_left < (long long)hdr->str_off + hdr->str_len) {
-		pr_debug("Invalid BTF total size:%u\n", btf->raw_size);
+		pr_debug("Invalid BTF total size: %u\n", btf->raw_size);
 		return -EINVAL;
 	}
 
-- 
2.33.0