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Wed, 15 Oct 2025 23:39:56 -0700 (PDT) Received: from localhost.localdomain ([2409:891f:1d64:636e:f4f7:9293:7b0c:3078]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-29099b0215esm17555295ad.112.2025.10.15.23.39.51 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 15 Oct 2025 23:39:55 -0700 (PDT) From: Yafang Shao To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org Cc: bpf@vger.kernel.org, linux-mm@kvack.org, Yafang Shao , Lorenzo Stoakes Subject: [PATCH bpf-next 1/2] bpf: mark mm->owner as __safe_rcu_or_null Date: Thu, 16 Oct 2025 14:39:28 +0800 Message-Id: <20251016063929.13830-2-laoar.shao@gmail.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20251016063929.13830-1-laoar.shao@gmail.com> References: <20251016063929.13830-1-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 72071A0006 X-Stat-Signature: q8ed6qxib3j6fcc6uhcg9858tgrmm35s X-Rspam-User: X-HE-Tag: 1760596797-327550 X-HE-Meta: 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 4ockBwRn 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When CONFIG_MEMCG is enabled, we can access mm->owner under RCU. The owner can be NULL. With this change, BPF helpers can safely access mm->owner to retrieve the associated task from the mm. We can then make policy decision based on the task attribute. The typical use case is as follows, bpf_rcu_read_lock(); // rcu lock must be held for rcu trusted field @owner = @mm->owner; // mm_struct::owner is rcu trusted or null if (!@owner) goto out; /* Do something based on the task attribute */ out: bpf_rcu_read_unlock(); Suggested-by: Andrii Nakryiko Signed-off-by: Yafang Shao Acked-by: Lorenzo Stoakes --- kernel/bpf/verifier.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c908015b2d34..d0adf5600c4d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7054,6 +7054,9 @@ BTF_TYPE_SAFE_RCU(struct cgroup_subsys_state) { /* RCU trusted: these fields are trusted in RCU CS and can be NULL */ BTF_TYPE_SAFE_RCU_OR_NULL(struct mm_struct) { struct file __rcu *exe_file; +#ifdef CONFIG_MEMCG + struct task_struct __rcu *owner; +#endif }; /* skb->sk, req->sk are not RCU protected, but we mark them as such -- 2.47.3