linux-kernel - [PATCH bpf] libbpf: Fix OOB read in btf_dump_get_bitfield

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20260106233527.163487-1-varunrmallya@gmail.com>
Date: Wed,  7 Jan 2026 05:05:27 +0530
From: Varun R Mallya <varunrmallya@...il.com>
To: andrii@...nel.org,
	alan.maguire@...cle.com
Cc: ast@...nel.org,
	daniel@...earbox.net,
	bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	varunrmallya@...il.com,
	Harrison Green <harrisonmichaelgreen@...il.com>
Subject: [PATCH bpf] libbpf: Fix OOB read in btf_dump_get_bitfield_value

When dumping bitfield data, btf_dump_get_bitfield_value() reads data
based on the underlying type's size (t->size). However, it does not
verify that the provided data buffer (data_sz) is large enough to
contain these bytes.

If btf_dump__dump_type_data() is called with a buffer smaller than
the type's size, this leads to an out-of-bounds read. This was
confirmed by AddressSanitizer in the linked issue.

Fix this by ensuring we do not read past the provided data_sz limit.

Fixes: a1d3cc3c5eca ("libbpf: Avoid use of __int128 in typed dump display")
Reported-by: Harrison Green <harrisonmichaelgreen@...il.com>
Closes: https://github.com/libbpf/libbpf/issues/928
Suggested-by: Alan Maguire <alan.maguire@...cle.com>
Signed-off-by: Varun R Mallya <varunrmallya@...il.com>
---
 tools/lib/bpf/btf_dump.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 6388392f49a0..53c6624161d7 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -1762,9 +1762,18 @@ static int btf_dump_get_bitfield_value(struct btf_dump *d,
 	__u16 left_shift_bits, right_shift_bits;
 	const __u8 *bytes = data;
 	__u8 nr_copy_bits;
+	__u8 start_bit, nr_bytes;
 	__u64 num = 0;
 	int i;
 
+	/* Calculate how many bytes cover the bitfield */
+	start_bit = bits_offset % 8;
+	nr_bytes = (start_bit + bit_sz + 7) / 8;
+
+	/* Bound check */
+	if (data + nr_bytes > d->typed_dump->data_end)
+		return -E2BIG;
+
 	/* Maximum supported bitfield size is 64 bits */
 	if (t->size > 8) {
 		pr_warn("unexpected bitfield size %d\n", t->size);
-- 
2.52.0