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Fri, 23 Oct 2026 14:14:35 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id M74QHstr22rOeQAAD6G6ig (envelope-from ); Fri, 23 Oct 2026 14:14:35 +0000 Message-ID: <30d58956-89b3-458e-bff8-69cd86f38415@suse.de> Date: Fri, 23 Oct 2026 16:13:33 +0200 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net 3/5] ipv6: restrict mld_qrv to 255 To: Jiayuan Chen , netdev@vger.kernel.org Cc: stable@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , David Ahern , Ido Schimmel , Kuniyuki Iwashima , Neal Cardwell , Joel Granados , Chia-Yu Chang , Wyatt Feng , Yung Chih Su , Flavio Leitner , Hannes Frederic Sowa , "Paul E. McKenney" , Petr Mladek , linux-kernel@vger.kernel.org References: <20261023091419.167088-1-jiayuan.chen@linux.dev> <20261023091419.167088-4-jiayuan.chen@linux.dev> Content-Language: en-US From: Fernando Fernandez Mancera In-Reply-To: <20261023091419.167088-4-jiayuan.chen@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spamd-Result: default: False [-13.29 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; XM_UA_NO_VERSION(0.01)[]; RCVD_TLS_ALL(0.00)[]; RCPT_COUNT_TWELVE(0.00)[21]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com,icloud.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[vger.kernel.org,davemloft.net,kernel.org,redhat.com,nvidia.com,google.com,nokia-bell-labs.com,icloud.com,gmail.com,stressinduktion.org,suse.com]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,imap1.dmz-prg2.suse.org:helo] X-Spam-Score: -13.29 X-Spam-Level: X-Spam-Flag: NO On 10/23/26 11:13 AM, Jiayuan Chen wrote: > net.ipv6.mld_qrv only has a lower bound, but ipv6_mc_reset() stores it > into the u8 inet6_dev::mc_qrv, and every MLD retransmit counter derived > from it (mca_crcount, sf_crcount, mc_ifc_count, mc_dad_count) is u8 as > well. Anything above 255 silently wraps: 256 becomes 0, so no state > change report is ever retransmitted, and the first MLDv2 Query received > on the interface then trips the WARN_ON() in mld_update_qrv(): > > WARN_ON(idev->mc_qrv == 0); > > A plain bridge with mcast_querier enabled on the link is enough: > > WARNING: net/ipv6/mcast.c:1327 at mld_query_work+0x1fd2/0x2cb0, CPU#3: kworker/3:1/2688 > Workqueue: mld mld_query_work > RIP: 0010:mld_query_work+0x1fd2/0x2cb0 > Call Trace: > > process_one_work+0x93a/0x1b20 > worker_thread+0x6d0/0x11d0 > kthread+0x358/0x470 > ret_from_fork+0x5b3/0x820 > ret_from_fork_asm+0x1a/0x30 > > > Cap the sysctl at U8_MAX, the largest value mc_qrv can actually hold. > > Fixes: 2f711939d2ea ("ipv6: add sysctl_mld_qrv to configure query robustness variable") > Cc: stable@vger.kernel.org > Signed-off-by: Jiayuan Chen Reviewed-by: Fernando Fernandez Mancera Thanks!