> On Nov 2, 2020, at 9:18 PM, Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Mon, Nov 2, 2020 at 4:51 PM Song Liu <songliubraving@xxxxxx> wrote:
>>
>>
>>
>>> On Oct 28, 2020, at 5:58 PM, Andrii Nakryiko <andrii@xxxxxxxxxx> wrote:
>>>
>>> Make data section layout checks stricter, disallowing overlap of types and
>>> strings data.
>>>
>>> Additionally, allow BTFs with no type data. There is nothing inherently wrong
>>> with having BTF with no types (put potentially with some strings). This could
>>> be a situation with kernel module BTFs, if module doesn't introduce any new
>>> type information.
>>>
>>> Also fix invalid offset alignment check for btf->hdr->type_off.
>>>
>>> Fixes: 8a138aed4a80 ("bpf: btf: Add BTF support to libbpf")
>>> Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
>>> ---
>>> tools/lib/bpf/btf.c | 16 ++++++----------
>>> 1 file changed, 6 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
>>> index 20c64a8441a8..9b0ef71a03d0 100644
>>> --- a/tools/lib/bpf/btf.c
>>> +++ b/tools/lib/bpf/btf.c
>>> @@ -245,22 +245,18 @@ static int btf_parse_hdr(struct btf *btf)
>>> return -EINVAL;
>>> }
>>>
>>> - if (meta_left < hdr->type_off) {
>>> - pr_debug("Invalid BTF type section offset:%u\n", hdr->type_off);
>>> + if (meta_left < hdr->str_off + hdr->str_len) {
>>> + pr_debug("Invalid BTF total size:%u\n", btf->raw_size);
>>> return -EINVAL;
>>> }
>>
>> Can we make this one as
>> if (meta_left != hdr->str_off + hdr->str_len) {
>
> That would be not forward-compatible. I.e., old libbpf loading new BTF
> with extra stuff after the string section. Kernel is necessarily more
> strict, but I'd like to keep libbpf more permissive with this.
Yeah, this makes sense. Let's keep both checks AS-IS.
Thanks,
Song
