Struct oom_control is used to describe the OOM context.
It's memcg field defines the scope of OOM: it's NULL for global
OOMs and a valid memcg pointer for memcg-scoped OOMs.
Teach bpf verifier to recognize it as trusted or NULL pointer.
It will provide the bpf OOM handler a trusted memcg pointer,
which for example is required for iterating the memcg's subtree.

Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/verifier.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 542e23fb19c7..811275419be3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7104,6 +7104,10 @@ BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct vm_area_struct) {
 	struct file *vm_file;
 };
 
+BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct oom_control) {
+	struct mem_cgroup *memcg;
+};
+
 static bool type_is_rcu(struct bpf_verifier_env *env,
 			struct bpf_reg_state *reg,
 			const char *field_name, u32 btf_id)
@@ -7146,6 +7150,7 @@ static bool type_is_trusted_or_null(struct bpf_verifier_env *env,
 	BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct socket));
 	BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct dentry));
 	BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct vm_area_struct));
+	BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct oom_control));
 
 	return btf_nested_type_is_trusted(&env->log, reg, field_name, btf_id,
 					  "__safe_trusted_or_null");
-- 
2.51.0