From 5714ca8cba5ed736f3733663c446cbee63a10a64 Mon Sep 17 00:00:00 2001 From: Varun R Mallya Date: Wed, 7 Jan 2026 05:05:27 +0530 Subject: [PATCH] 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 Suggested-by: Alan Maguire Signed-off-by: Varun R Mallya Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260106233527.163487-1-varunrmallya@gmail.com Closes: https://github.com/libbpf/libbpf/issues/928 --- 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 6388392f49a0b..53c6624161d79 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); -- 2.47.3