[PATCH bpf-next v4 11/20] bpf, lsm: Add disabled BPF LSM hook list

Xu Kuohai
2024-07-11T11:14:02Z

From: Xu Kuohai <xukuohai@huawei.com>

Add a disabled hooks list for BPF LSM. progs being attached to the
listed hooks will be rejected by the verifier.

Suggested-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
---
kernel/bpf/bpf_lsm.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 08a338e1f231..e5feb6560fe6 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -36,6 +36,12 @@ BTF_SET_START(bpf_lsm_hooks)
#undef LSM_HOOK
BTF_SET_END(bpf_lsm_hooks)

+BTF_SET_START(bpf_lsm_disabled_hooks)
+BTF_ID(func, bpf_lsm_getprocattr)
+BTF_ID(func, bpf_lsm_setprocattr)
+BTF_ID(func, bpf_lsm_ismaclabel)
+BTF_SET_END(bpf_lsm_disabled_hooks)
+
/* List of LSM hooks that should operate on 'current' cgroup regardless
* of function signature.
*/
@@ -97,15 +103,24 @@ void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog,
int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
const struct bpf_prog *prog)
{
+ u32 btf_id = prog->aux->attach_btf_id;
+ const char *func_name = prog->aux->attach_func_name;
+
if (!prog->gpl_compatible) {
bpf_log(vlog,
"LSM programs must have a GPL compatible license\n");
return -EINVAL;
}

- if (!btf_id_set_contains(&bpf_lsm_hooks, prog->aux->attach_btf_id)) {
+ if (btf_id_set_contains(&bpf_lsm_disabled_hooks, btf_id)) {
+ bpf_log(vlog, "attach_btf_id %u points to disabled hook %s\n",
+ btf_id, func_name);
+ return -EINVAL;
+ }
+
+ if (!btf_id_set_contains(&bpf_lsm_hooks, btf_id)) {
bpf_log(vlog, "attach_btf_id %u points to wrong type name %s\n",
- prog->aux->attach_btf_id, prog->aux->attach_func_name);
+ btf_id, func_name);
return -EINVAL;
}

--
2.30.2