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[2a03:2880:30ff:3::face:b00c]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-aa4f418018csm90855766b.62.2024.11.21.06.59.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Nov 2024 06:59:01 -0800 (PST) From: Breno Leitao Date: Thu, 21 Nov 2024 06:58:58 -0800 Subject: [PATCH net] netpoll: Use rtnl_dereference() for npinfo pointer access Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20241121-netpoll_rcu_herbet_fix-v1-1-457c5fee9dfd@debian.org> X-B4-Tracking: v=1; b=H4sIALJKP2cC/x3MWwqDMBAF0K0M99tAHtKWbKWUoHZSByTKJBZB3 HuhZwHnRGUVroh0QvkrVdaCSK4jTPNQPmzkjUjw1vfOeWcKt21dlqTTnmbWkVvKcpiQ7dCHMN4 fN4uOsClnOf7xE4UbXtf1A1zdZEhtAAAA X-Change-ID: 20241121-netpoll_rcu_herbet_fix-3f0a433b7860 To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Michal Kubiak Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Herbert Xu , Breno Leitao X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=1673; i=leitao@debian.org; h=from:subject:message-id; bh=4Ti8G1SA/x6VmROm/Eqi+j3OT/kIiBi+z8sE2UMstog=; b=owEBbQKS/ZANAwAIATWjk5/8eHdtAcsmYgBnP0q0rCJDyc2+J04wAirfAEZ7EnhcHNuByBGNG iaVT56lJiOJAjMEAAEIAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCZz9KtAAKCRA1o5Of/Hh3 bSJwEACSC+5nfj70NnIaTRlIaTq8YGHq8fW3x5nXbsAQ5PG8VwMDHmDEXLeZ1UKoodZHzE55Rjd cvcDGLNeo3SSh/WXKeR9ZfPGCxp95AaPIRro9pLRUffDtnVPi0N5PLafyKVAOL2ej2Ut7KAm3C/ bN6PhpHpNGJf3oEoO9j/v3h9zD0HG7LfUwiJSydvOcwg/jfT4fLULcFXhoyhyBD28abKbcXVys/ yYIqGwExSb1G44DN598Ax4jdUbhOFBFxlqZACG/7smcUpeXu4BUyNPR5j3O+T7glvrKjXXsv5DE L1wsDdInmJdD6hqRaNmBWuRw3bwDa9X8TIlpFIbY1bQ8mmP+oUkkZh310LoPDJ67rWCbZDkAB/q IBYn86dUSx5b17FMYBupaun04mWPLr8uElkzsNgFwhhojFWRdpNwRgX+v+U+E0McOmIJy3S6Iip lkj0E5kUzIkVTXwAWUWhZO6FRnaOA0R3I3drQxxsGVILIZmc8ubDbbvIl6FMT48GlkiwY3Wux24 9EwVWUtJpfrFiQAcTavSCt1wOp6a4iIy5x6lucEb+dGg+0tI/4iQjrw6s7U0n/LLvFy9d/mrkwW m0bJrCtVZqwbxdHmquh/tMrC1H2Vsnlb7bIWpfjGevn0nSdwzLiJOXIBDcupyg6j2wEEu9rGZSr 8lTVf40nrm2KJ9g== X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D In the __netpoll_setup() function, when accessing the device's npinfo pointer, replace rcu_access_pointer() with rtnl_dereference(). This change is more appropriate, as suggested by Herbert Xu. The function is called with the RTNL mutex held, and the pointer is being dereferenced later, so, dereference earlier and just reuse the pointer for the if/else. The replacement ensures correct pointer access while maintaining the existing locking and RCU semantics of the netpoll subsystem. Fixes: c75964e40e69 ("netpoll: Use rtnl_dereference() for npinfo pointer ac= cess") Suggested-by: Herbert Xu Signed-off-by: Breno Leitao Acked-by: Herbert Xu Reviewed-by: Jacob Keller --- net/core/netpoll.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/core/netpoll.c b/net/core/netpoll.c index 45fb60bc4803958eb07d4038028269fc0c19622e..30152811e0903a369ccca30500e= 11e696be158fd 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -626,7 +626,8 @@ int __netpoll_setup(struct netpoll *np, struct net_devi= ce *ndev) goto out; } =20 - if (!rcu_access_pointer(ndev->npinfo)) { + npinfo =3D rtnl_dereference(ndev->npinfo); + if (!npinfo) { npinfo =3D kmalloc(sizeof(*npinfo), GFP_KERNEL); if (!npinfo) { err =3D -ENOMEM; @@ -646,7 +647,6 @@ int __netpoll_setup(struct netpoll *np, struct net_devi= ce *ndev) goto free_npinfo; } } else { - npinfo =3D rtnl_dereference(ndev->npinfo); refcount_inc(&npinfo->refcnt); } =20 --- base-commit: 66418447d27b7f4c027587582a133dd0bc0a663b change-id: 20241121-netpoll_rcu_herbet_fix-3f0a433b7860 Best regards, --=20 Breno Leitao