[PATCH bpf-next v3 2/8] bpf: allow helpers to return PTR_TO_SOCK_COMMON

[Lorenz Bauer]

It's currently not possible to access timewait or request sockets
from eBPF, since there is no way to return a PTR_TO_SOCK_COMMON
from a helper. Introduce RET_PTR_TO_SOCK_COMMON to enable this
behaviour.

Signed-off-by: Lorenz Bauer <l...@cloudflare.com>
---
 include/linux/bpf.h   | 1 +
 kernel/bpf/verifier.c | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f02367faa58d..f62897198844 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -205,6 +205,7 @@ enum bpf_return_type {
        RET_PTR_TO_MAP_VALUE_OR_NULL,   /* returns a pointer to map elem value 
or NULL */
        RET_PTR_TO_SOCKET_OR_NULL,      /* returns a pointer to a socket or 
NULL */
        RET_PTR_TO_TCP_SOCK_OR_NULL,    /* returns a pointer to a tcp_sock or 
NULL */
+       RET_PTR_TO_SOCK_COMMON_OR_NULL, /* returns a pointer to a sock_common 
or NULL */
 };
 
 /* eBPF function prototype used by verifier to allow BPF_CALLs from eBPF 
programs
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 868a82ad5597..a476e13201d6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3148,6 +3148,10 @@ static int check_helper_call(struct bpf_verifier_env 
*env, int func_id, int insn
                mark_reg_known_zero(env, regs, BPF_REG_0);
                regs[BPF_REG_0].type = PTR_TO_SOCKET_OR_NULL;
                regs[BPF_REG_0].id = ++env->id_gen;
+       } else if (fn->ret_type == RET_PTR_TO_SOCK_COMMON_OR_NULL) {
+               mark_reg_known_zero(env, regs, BPF_REG_0);
+               regs[BPF_REG_0].type = PTR_TO_SOCK_COMMON_OR_NULL;
+               regs[BPF_REG_0].id = ++env->id_gen;
        } else if (fn->ret_type == RET_PTR_TO_TCP_SOCK_OR_NULL) {
                mark_reg_known_zero(env, regs, BPF_REG_0);
                regs[BPF_REG_0].type = PTR_TO_TCP_SOCK_OR_NULL;
-- 
2.19.1