[PATCH bpf-next v4 3/4] bpf: Pass const struct bpf_prog * to .check_member

David Vernet
2023-01-25T16:47:59Z

The .check_member field of struct bpf_struct_ops is currently passed the
member's btf_type via const struct btf_type *t, and a const struct
btf_member *member. This allows the struct_ops implementation to check
whether e.g. an ops is supported, but it would be useful to also enforce
that the struct_ops prog being loaded for that member has other
qualities, like being sleepable (or not). This patch therefore updates
the .check_member() callback to also take a const struct bpf_prog *prog
argument.

Signed-off-by: David Vernet <void@manifault.com>
---
include/linux/bpf.h | 3 ++-
kernel/bpf/verifier.c | 2 +-
net/ipv4/bpf_tcp_ca.c | 3 ++-
3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 1bec48d9e5d9..0d868ef1b973 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1422,7 +1422,8 @@ struct bpf_struct_ops {
const struct bpf_verifier_ops *verifier_ops;
int (*init)(struct btf *btf);
int (*check_member)(const struct btf_type *t,
- const struct btf_member *member);
+ const struct btf_member *member,
+ const struct bpf_prog *prog);
int (*init_member)(const struct btf_type *t,
const struct btf_member *member,
void *kdata, const void *udata);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c8907df49f81..6bd097e0d45f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -16792,7 +16792,7 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
}

if (st_ops->check_member) {
- int err = st_ops->check_member(t, member);
+ int err = st_ops->check_member(t, member, prog);

if (err) {
verbose(env, "attach to unsupported member %s of struct %s\n",
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 4517d2bd186a..13fc0c185cd9 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -248,7 +248,8 @@ static int bpf_tcp_ca_init_member(const struct btf_type *t,
}

static int bpf_tcp_ca_check_member(const struct btf_type *t,
- const struct btf_member *member)
+ const struct btf_member *member,
+ const struct bpf_prog *prog)
{
if (is_unsupported(__btf_member_bit_offset(t, member) / 8))
return -ENOTSUPP;
--
2.39.0