On Fri, Jul 29, 2022 at 05:08:08PM -0700, Stanislav Fomichev wrote:
> When attaching to program, the program itself might not be attached
> to anything (and, hence, might not have attach_btf), so we can't
> unconditionally use 'prog->aux->dst_prog->aux->attach_btf'.
> Instead, use bpf_prog_get_target_btf to pick proper target btf:
>
> * when attached to dst_prog, use dst_prog->aux->btf
> * when attached to kernel btf, use prog->aux->attach_btf
>
> Fixes: b79c9fc9551b ("bpf: implement BPF_PROG_QUERY for BPF_LSM_CGROUP")
> Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
> ---
> kernel/bpf/syscall.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 83c7136c5788..7dc3f8003631 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -3886,6 +3886,7 @@ static int bpf_prog_get_info_by_fd(struct file *file,
> union bpf_attr __user *uattr)
> {
> struct bpf_prog_info __user *uinfo = u64_to_user_ptr(attr->info.info);
> + struct btf *attach_btf = bpf_prog_get_target_btf(prog);
> struct bpf_prog_info info;
> u32 info_len = attr->info.info_len;
> struct bpf_prog_kstats stats;
> @@ -4088,10 +4089,8 @@ static int bpf_prog_get_info_by_fd(struct file *file,
> if (prog->aux->btf)
> info.btf_id = btf_obj_id(prog->aux->btf);
> info.attach_btf_id = prog->aux->attach_btf_id;
> - if (prog->aux->attach_btf)
> - info.attach_btf_obj_id = btf_obj_id(prog->aux->attach_btf);
> - else if (prog->aux->dst_prog)
> - info.attach_btf_obj_id = btf_obj_id(prog->aux->dst_prog->aux->attach_btf);
> + if (attach_btf)
> + info.attach_btf_obj_id = btf_obj_id(attach_btf);
Nice.
Acked-by: Martin KaFai Lau <kafai@xxxxxx>
