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[35.200.156.90]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36a429018casm11668877eec.14.2026.10.30.22.46.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Oct 2026 22:46:38 -0700 (PDT) From: Anil Kaushik To: netdev@vger.kernel.org Cc: "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Ido Schimmel , Nicolas Dichtel , Jacob Keller , Jiri Pirko , XingWang Xiang , Alice Ryhl , linux-kernel@vger.kernel.org Subject: [PATCH net v2 0/2] genetlink: fix joining multicast groups no family owns Date: Sat, 31 Oct 2026 05:46:30 +0000 Message-Id: <20261031054632.3697295-1-anilkaushikwireless@gmail.com> X-Mailer: git-send-email 2.25.1 X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit genl_bind() checks the GENL_MCAST_CAP_* flags of a group only when a family owns it. A socket can join a free group ID and stay a member when a family with those flags gets the ID later. Patch 1 rejects joins to group IDs that no family owns. Patch 2 clears the members of the group IDs when a family is given them. This covers the race Sashiko found on v1, where the family is unregistered between genl_bind() and the point where the membership bit is set. One case is left. If the family is unregistered and a family with GENL_MCAST_CAP_* flags gets the ID, both inside that window, the bit is set after the clear. Closing it needs the check and the update under one lock in af_netlink.c. I will send that separately. Tested as an unprivileged user, with an msleep() added after the bind callback in netlink_setsockopt() and a test family that registers again with GENL_MCAST_CAP_NET_ADMIN: v1 v2 unregister in the window, register later member not member unregister and register in the window member member The test from v1 (join all free IDs, then load gtp and drop_monitor) gives the same result as before, and patch 2 alone also fixes it. Changes in v2: - New patch 2 (Sashiko). - Patch 1: no change, added Reviewed-by tags. v1: https://lore.kernel.org/netdev/20261029062214.3407223-1-anilkaushikwireless@gmail.com/ Anil Kaushik (2): genetlink: Reject joining multicast groups no family owns genetlink: Clear stale members when assigning multicast group IDs net/netlink/genetlink.c | 34 +++++++++++++++++++++++----------- 1 file changed, 23 insertions(+), 11 deletions(-) -- 2.25.1