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([2a01:e0a:ab7:2110:6a1d:efff:fe52:1959]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-490bc3918fcsm624698755e9.3.2026.06.10.00.50.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 Jun 2026 00:50:11 -0700 (PDT) Message-ID: Date: Wed, 10 Jun 2026 09:50:10 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: nicolas.dichtel@6wind.com Subject: Re: [PATCH net-next] ipv4: igmp: remove multicast group from hash table on device destruction To: Yuyang Huang Cc: "David S. Miller" , David Ahern , Eric Dumazet , Ido Schimmel , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-kernel@vger.kernel.org, netdev@vger.kernel.org References: <20260609122646.2297540-1-yuyanghuang@google.com> From: Nicolas Dichtel Content-Language: en-US Organization: 6WIND In-Reply-To: <20260609122646.2297540-1-yuyanghuang@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Le 09/06/2026 à 14:26, Yuyang Huang a écrit : > When a device is destroyed under RTNL, ip_mc_destroy_dev() iterates through > the multicast list and calls ip_ma_put() on each membership, scheduling > them for RCU reclamation. However, they are not unlinked from the device's > multicast hash table (mc_hash). > > Since the device remains published in dev->ip_ptr until after > ip_mc_destroy_dev() completes, concurrent RCU readers traversing mc_hash > can still locate and access the multicast group after its refcount is > decremented. If the RCU callback runs and frees the group while a reader is > accessing it, a use-after-free occurs. > > Fix this by unlinking the multicast group from mc_hash using > ip_mc_hash_remove() before scheduling it for reclamation. > > Signed-off-by: Yuyang Huang A 'Fixes' tag may be useful for backports. Regards, Nicolas