On 13 March 2024 17:39:14 GMT, Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote:
>On Wed, Mar 13, 2024 at 10:24 AM Quentin Monnet <quentin@xxxxxxxxxxxxx> wrote:
>>
>> This reverts commit df7c3f7d3a3ddab31ca8cfa9b86a8729ec43fd2e.
>>
>> There's no guarantee that obj->btf is non-NULL when passing it to
>> btf__fd(), and this function doesn't perform any check before
>> dereferencing its argument. As a consequence, this commit caused
>> segmentation faults in bpftool (for example) when trying to load
>> programs that come without BTF info.
>>
>> Signed-off-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
>> ---
>> tools/lib/bpf/libbpf.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index efab29b8935b..0f9a4d232468 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -7343,7 +7343,7 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog
>> load_attr.prog_ifindex = prog->prog_ifindex;
>>
>> /* specify func_info/line_info only if kernel supports them */
>> - btf_fd = btf__fd(obj->btf);
>> + btf_fd = bpf_object__btf_fd(obj);
>
>oh, my bad, sorry about that. But I'd still like to stick to using
>btf__fd(), so maybe let's fix forward by dropping btf_fd variable here
>and doing what bpf_object__create_map() does:
>
>if (obj->btf && btf__fd(obj->btf) >= 0 && kernel_supports(...)) {
> load_attr.prog_btf_fd = btf__fd(obj->btf);
> ...
>}
>
>?
I half-expected that :). I don't mind at all, I'll send an updated version tomorrow. Thanks!
