[bpf-next,v3,04/11] bpf, lsm: Add bpf lsm disabled hook list

Commit Message

Xu Kuohai April 11, 2024, 12:27 p.m. UTC

From: Xu Kuohai <[e-mail]>

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 <[e-mail]>
Signed-off-by: Xu Kuohai <[e-mail]>
---
 kernel/bpf/bpf_lsm.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

Patch

diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 4e1a4a333000..7f5648b404f2 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -68,6 +68,12 @@  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.
  */
@@ -129,15 +135,25 @@  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 bpf lsm 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;
 	}