linux-kernel - [PATCH rfc 02/12] bpf: mark struct oom_control's memcg field as TRUSTED_OR

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Message-ID: <20250428033617.3797686-3-roman.gushchin@linux.dev>
Date: Mon, 28 Apr 2025 03:36:07 +0000
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: linux-kernel@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Suren Baghdasaryan <surenb@...gle.com>,
	David Rientjes <rientjes@...gle.com>,
	Josh Don <joshdon@...gle.com>,
	Chuyi Zhou <zhouchuyi@...edance.com>,
	cgroups@...r.kernel.org,
	linux-mm@...ck.org,
	bpf@...r.kernel.org,
	Roman Gushchin <roman.gushchin@...ux.dev>
Subject: [PATCH rfc 02/12] bpf: mark struct oom_control's memcg field as TRUSTED_OR_NULL

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@...ux.dev>
---
 kernel/bpf/verifier.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 54c6953a8b84..d2d9f9b87065 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7047,6 +7047,10 @@ BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct socket) {
 	struct sock *sk;
 };
 
+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)
@@ -7087,6 +7091,7 @@ static bool type_is_trusted_or_null(struct bpf_verifier_env *env,
 				    const char *field_name, u32 btf_id)
 {
 	BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct socket));
+	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");
-- 
2.49.0.901.g37484f566f-goog