[PATCH v8 bpf-next 1/5] bpf: Allow "sk_buff" and "xdp_buff" as valid kfunc arg types

[Joanne Koong <joannelkoong@gmail.com>]

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 and __sk_buff, and xdp_buff and xdp_md to be
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. Please note that the
__sk_buff/xdp_md -> sk_buff/xdp_buff conversion happens in
convert_ctx_accesses() in the verifier.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 kernel/bpf/btf.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 47b8cb96f2c2..b4da17688c65 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5606,6 +5606,10 @@ btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
 	 * 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))
 		return NULL;
 	return ctx_type;
-- 
2.30.2