Subject: Re: [PATCH net-next v2 05/15] xdp: allow attaching programs loaded for specific device

From: Jiri Pirko <[email-masked]>
Date: Sun, 12 Nov 2017 10:00:41 +0100

Fri, Nov 03, 2017 at 09:56:20PM CET, [email-masked] wrote:
>Pass the netdev pointer to bpf_prog_get_type().  This way
>BPF code can decide whether the device matches what the
>code was loaded/translated for.
>

[...]

>diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
>index 3217c20ea91b..68f9123acd39 100644
>--- a/kernel/bpf/syscall.c
>+++ b/kernel/bpf/syscall.c
>@@ -1057,7 +1057,22 @@ struct bpf_prog *bpf_prog_inc_not_zero(struct bpf_prog *prog)
> }
> EXPORT_SYMBOL_GPL(bpf_prog_inc_not_zero);
> 
>-static struct bpf_prog *__bpf_prog_get(u32 ufd, enum bpf_prog_type *attach_type)
>+static bool bpf_prog_can_attach(struct bpf_prog *prog,
>+				enum bpf_prog_type *attach_type,
>+				struct net_device *netdev)
>+{
>+	struct bpf_dev_offload *offload = prog->aux->offload;
>+
>+	if (prog->type != *attach_type)
>+		return false;
>+	if (offload && offload->netdev != netdev)

This means you return false in case netdev function arg is NULL. Is that
intentional?

Seems wrong to me because for example in cls_bpf_prog_from_efd, you
would get an error in case TCA_CLS_FLAGS_SKIP_SW is not set.

>+		return false;
>+
>+	return true;
>+}