[PATCH 5.14 495/849] libbpf: Fix BTF header parsing checks

Greg Kroah-Hartman
2021-11-15T23:03:26Z

From: Andrii Nakryiko <andrii@kernel.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@ya.ru>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211023003157.726961-2-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.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 3e3ecac43ea9b..7ab9f702e72ac 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