[PATCH 5.15 503/917] libbpf: Fix overflow in BTF sanity checks

Greg Kroah-Hartman
2021-11-16T00:52:20Z

From: Andrii Nakryiko <andrii@kernel.org>

[ Upstream commit 5245dafe3d49efba4d3285cf27ee1cc1eeafafc6 ]

btf_header's str_off+str_len or type_off+type_len can overflow as they
are u32s. This will lead to bypassing the sanity checks during BTF
parsing, resulting in crashes afterwards. Fix by using 64-bit signed
integers for comparison.

Fixes: d8123624506c ("libbpf: Fix BTF data layout checks and allow empty BTF")
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/20211023003157.726961-1-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/lib/bpf/btf.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index bf8c8676d68e5..cfd701debcf61 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -236,12 +236,12 @@ static int btf_parse_hdr(struct btf *btf)
}

meta_left = btf->raw_size - sizeof(*hdr);
- if (meta_left < hdr->str_off + hdr->str_len) {
+ if (meta_left < (long long)hdr->str_off + hdr->str_len) {
pr_debug("Invalid BTF total size:%u\n", btf->raw_size);
return -EINVAL;
}

- if (hdr->type_off + hdr->type_len > hdr->str_off) {
+ if ((long long)hdr->type_off + hdr->type_len > hdr->str_off) {
pr_debug("Invalid BTF data sections layout: type data at %u + %u, strings data at %u + %u\n",
hdr->type_off, hdr->type_len, hdr->str_off, hdr->str_len);
return -EINVAL;
--
2.33.0