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[2a03:2880:30ff:8::face:b00c]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-aa20df779afsm526330666b.85.2024.11.18.03.15.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Nov 2024 03:15:25 -0800 (PST) From: Breno Leitao Subject: [PATCH net 0/2] netpoll: Use RCU primitives for npinfo pointer access Date: Mon, 18 Nov 2024 03:15:16 -0800 Message-Id: <20241118-netpoll_rcu-v1-0-a1888dcb4a02@debian.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAMQhO2cC/x3MawpAQBQG0K3cvt+m3MkjsxVJHhe3NDSDlOxdO Qs4D6IElQhHD4JcGnXzcMQJYVg6P4vREY5gU5sxc268HPu2rm0YTiM926rImfuSkRD2IJPe/1b Dy4HmfT/WCmIAYgAAAA== X-Change-ID: 20241115-netpoll_rcu-eb1296511b71 To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Herbert Xu , Stephen Hemminger Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Breno Leitao , paulmck@kernel.org X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=1263; i=leitao@debian.org; h=from:subject:message-id; bh=Fm7X1rCptseYOQiiHdn+GV/CEfNvRsjcmulihtwd6HY=; b=owEBbAKT/ZANAwAIATWjk5/8eHdtAcsmYgBnOyHMErtDbbsgRv7aBSysHxC9Yoro18RyV4IKP I3b2qvmEv2JAjIEAAEIAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCZzshzAAKCRA1o5Of/Hh3 bdc6D/dZwS2S3pxXkN5wfeusbymKpKl6epvnYa/pl3WJRSbh5e4kqNE+NG2HxoUD3QO29EqbCSk e0zVZUCj7mEYJg5OnwcEtByPsp+xYobSXomdM9dOy3CtVXfcnw58ztjukGItv4CtyJATWqNvGV7 5BeTwI5anP65Rm84SD05QbK+7hw8SM8GHG66659uASymBzLX0MSMQUpy4kyTX0L/G1J2xdCm5YD VqhKefrmZjqayoAmBUoSQN1DIMr8wrcODxGADdUB9a3W7qmEmpf99Cgux89DB6KvUa3p1pASsC6 6lpISEzC2krM3hNr/ddPOhJIgg+3/bfoST/F1yUE5eXQx078sPa32MN/5xmCuNMh5ks/aHy3KI5 LVAS5FL6FaxGUC5yj/vCQ1P9DFy/InpkzZ8OyWcgAGW+325af713+h5unzE8iv2dzFjes1s8orR FUb2HZKBf3Nk2ZZszuAAuZ8N6xNMLodsaERx1ZEQ4X/tGkx5jVSa2S1tw3GSyoIVAmFKKr+fKN+ /NZPgi50k4+iVGUmnHMmqyyw/BSFirnEhY6eZJskZe7SGT2IvSpwYGUQskIhVB6HsoMJSuG20Dz U5JPufRYbBCKpXMdudaOfnNYmkQr4zDMQHDNcdXVmUT29DNsoSp7MyrIiFWbD8uiBTCIYGQd8lX X8VjDgf/o9oFj X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D X-Patchwork-Delegate: kuba@kernel.org The net_device->npinfo pointer is marked with __rcu, indicating it requires proper RCU access primitives: struct net_device { ... struct netpoll_info __rcu *npinfo; ... }; Direct access to this pointer can lead to issues such as: - Compiler incorrectly caching/reusing stale pointer values - Missing memory ordering guarantees - Non-atomic pointer loads Replace direct NULL checks of npinfo with rcu_access_pointer(), which provides the necessary memory ordering guarantees without the overhead of a full RCU dereference, since we only need to verify if the pointer is NULL. In both cases, the RCU read lock is not held when the function is being called. I checked that by using lockdep_assert_in_rcu_read_lock(), and seeing the warning on both cases. Signed-off-by: Breno Leitao --- Breno Leitao (2): netpoll: Use rcu_access_pointer() in __netpoll_setup netpoll: Use rcu_access_pointer() in netpoll_poll_lock include/linux/netpoll.h | 2 +- net/core/netpoll.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) --- base-commit: 8ffade77b6337a8767fae9820d57d7a6413dd1a1 change-id: 20241115-netpoll_rcu-eb1296511b71 Best regards,