bpf: Support "sk_buff" and "xdp_buff" as valid kfunc arg types

The bpf mirror of the in-kernel sk_buff and xdp_buff data structures are
__sk_buff and xdp_md. Currently, when we pass in the program ctx to a
kfunc where the program ctx is a skb or xdp buffer, we reject the
program if the in-kernel definition is sk_buff/xdp_buff instead of
__sk_buff/xdp_md.

This change allows "sk_buff <--> __sk_buff" and "xdp_buff <--> xdp_md"
to be recognized as valid matches. The user program may pass in their
program ctx as a __sk_buff or xdp_md, and the in-kernel definition
of the kfunc may define this arg as a sk_buff or xdp_buff.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/r/20230301154953.641654-2-joannelkoong@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index fa22ec7..84cca84 100644 (file)
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5683,6 +5683,10 @@ again:
         * int socket_filter_bpf_prog(struct __sk_buff *skb)
         * { // no fields of skb are ever used }
         */
+       if (strcmp(ctx_tname, "__sk_buff") == 0 && strcmp(tname, "sk_buff") == 0)
+               return ctx_type;
+       if (strcmp(ctx_tname, "xdp_md") == 0 && strcmp(tname, "xdp_buff") == 0)
+               return ctx_type;
        if (strcmp(ctx_tname, tname)) {
                /* bpf_user_pt_regs_t is a typedef, so resolve it to
                 * underlying struct and check name again