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Fri, 26 Sep 2025 02:34:47 -0700 (PDT) From: Yafang Shao To: akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, hannes@cmpxchg.org, usamaarif642@gmail.com, gutierrez.asier@huawei-partners.com, willy@infradead.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, ameryhung@gmail.com, rientjes@google.com, corbet@lwn.net, 21cnbao@gmail.com, shakeel.butt@linux.dev, tj@kernel.org, lance.yang@linux.dev Cc: bpf@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Yafang Shao Subject: [PATCH v8 mm-new 07/12] bpf: mark mm->owner as __safe_rcu_or_null Date: Fri, 26 Sep 2025 17:33:38 +0800 Message-Id: <20250926093343.1000-8-laoar.shao@gmail.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20250926093343.1000-1-laoar.shao@gmail.com> References: <20250926093343.1000-1-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 21E8A180009 X-Rspamd-Server: rspam05 X-Stat-Signature: tsozu85ieo1anj739hidwidr4eghar78 X-Rspam-User: X-HE-Tag: 1758879288-895521 X-HE-Meta: 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 tMZDgOy4 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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 c4f69a9e9af6..d400e18ee31e 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7123,6 +7123,9 @@ 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