> On Nov 14, 2019, at 10:57 AM, Alexei Starovoitov <ast@xxxxxxxxxx> wrote:
>
> Annotate BPF program context types with program-side type and kernel-side type.
> This type information is used by the verifier. btf_get_prog_ctx_type() is
> used in the later patches to verify that BTF type of ctx in BPF program matches to
> kernel expected ctx type. For example, the XDP program type is:
> BPF_PROG_TYPE(BPF_PROG_TYPE_XDP, xdp, struct xdp_md, struct xdp_buff)
> That means that XDP program should be written as:
> int xdp_prog(struct xdp_md *ctx) { ... }
>
> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
>
[...]
> + /* only compare that prog's ctx type name is the same as
> + * kernel expects. No need to compare field by field.
> + * It's ok for bpf prog to do:
> + * struct __sk_buff {};
> + * int socket_filter_bpf_prog(struct __sk_buff *skb)
> + * { // no fields of skb are ever used }
> + */
> + if (strcmp(ctx_tname, tname))
> + return NULL;
Do we need to check size of the two struct? I guess we should not
allow something like
struct __sk_buff {
char data[REALLY_BIG_NUM];
};
int socket_filter_bpf_prog(struct __sk_buff *skb)
{ /* access end of skb */ }
Or did I miss the size check?
Thanks,
Song
