From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AA651403EA1; Tue, 21 Jul 2026 23:00:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784674850; cv=none; b=VSYxrla30YiWNLHIpWZzI8tl9KMFlM4G8RV9mXW5ex52t7SaC7Gt+1flUG4IwThA/wQLkvWS149hY1lvwLvZ3BSbcGnH2gLsSglZHb968GsPwcrlcg4GohMTkBeTtBmiYVh9PU8yYXihgRozh8sUHw4Yp6Wd6kqc1EG9y7pphco= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784674850; c=relaxed/simple; bh=RAKtnLvW6vZ2Mw4ZrQWqInEdwW4+9HIWVbLHMRMd2EI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JZh4zcYV9izVk5ZlW7+PBPqfSKeVERZzQQc8+zrxHzq+DKuO4tdhzFe4K2neEXnHmO+IGBa7q3BMh5+VJc4FIM6ftu855ny9VfYjEZonbSzEZtOxfEeWjTvVmYfXI9ss8PB95LLxWglinXfmOr54bzNw/yS6znpOPTkMFoSxVjI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=dVW8GR1J; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="dVW8GR1J" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 217DC1F000E9; Tue, 21 Jul 2026 23:00:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784674849; bh=3+ir1ffahwvp76+Qo+u1ZoO8ejnNPxvIEcjopnetyaw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dVW8GR1J+AFI2cdQBOj4rExXpFtFsELZ6KYUnVp1BsxlBGXUALYrbyWhqUMtxwc5A tLgEmgRMDJM2ylHafaGAP6E9rEe0jm1ntjN0LEZlEkrDWi+wKIGDP74KP6ikaX37rX tNTljx3QlD4VVEX0F8BBPHqWFgx8wnr7VjnMdN1w= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+a9400cabb1d784e49abf@syzkaller.appspotmail.com, Nikita Zhandarovich , Taehee Yoo , Eric Dumazet , Hangbin Liu , Jakub Kicinski Subject: [PATCH 5.10 697/699] ipv6: mcast: fix data-race in ipv6_mc_down / mld_ifc_work Date: Tue, 21 Jul 2026 17:27:36 +0200 Message-ID: <20260721152411.501575851@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152355.667394603@linuxfoundation.org> References: <20260721152355.667394603@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nikita Zhandarovich commit 2e7ef287f07c74985f1bf2858bedc62bd9ebf155 upstream. idev->mc_ifc_count can be written over without proper locking. Originally found by syzbot [1], fix this issue by encapsulating calls to mld_ifc_stop_work() (and mld_gq_stop_work() for good measure) with mutex_lock() and mutex_unlock() accordingly as these functions should only be called with mc_lock per their declarations. [1] BUG: KCSAN: data-race in ipv6_mc_down / mld_ifc_work write to 0xffff88813a80c832 of 1 bytes by task 3771 on cpu 0: mld_ifc_stop_work net/ipv6/mcast.c:1080 [inline] ipv6_mc_down+0x10a/0x280 net/ipv6/mcast.c:2725 addrconf_ifdown+0xe32/0xf10 net/ipv6/addrconf.c:3949 addrconf_notify+0x310/0x980 notifier_call_chain kernel/notifier.c:93 [inline] raw_notifier_call_chain+0x6b/0x1c0 kernel/notifier.c:461 __dev_notify_flags+0x205/0x3d0 dev_change_flags+0xab/0xd0 net/core/dev.c:8685 do_setlink+0x9f6/0x2430 net/core/rtnetlink.c:2916 rtnl_group_changelink net/core/rtnetlink.c:3458 [inline] __rtnl_newlink net/core/rtnetlink.c:3717 [inline] rtnl_newlink+0xbb3/0x1670 net/core/rtnetlink.c:3754 rtnetlink_rcv_msg+0x807/0x8c0 net/core/rtnetlink.c:6558 netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2545 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6576 netlink_unicast_kernel net/netlink/af_netlink.c:1342 [inline] netlink_unicast+0x589/0x650 net/netlink/af_netlink.c:1368 netlink_sendmsg+0x66e/0x770 net/netlink/af_netlink.c:1910 ... write to 0xffff88813a80c832 of 1 bytes by task 22 on cpu 1: mld_ifc_work+0x54c/0x7b0 net/ipv6/mcast.c:2653 process_one_work kernel/workqueue.c:2627 [inline] process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2700 worker_thread+0x525/0x730 kernel/workqueue.c:2781 ... Fixes: 2d9a93b4902b ("mld: convert from timer to delayed work") Reported-by: syzbot+a9400cabb1d784e49abf@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/000000000000994e09060ebcdffb@google.com/ Signed-off-by: Nikita Zhandarovich Acked-by: Taehee Yoo Reviewed-by: Eric Dumazet Reviewed-by: Hangbin Liu Link: https://lore.kernel.org/r/20240117172102.12001-1-n.zhandarovich@fintech.ru Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/ipv6/mcast.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/net/ipv6/mcast.c +++ b/net/ipv6/mcast.c @@ -2754,8 +2754,12 @@ void ipv6_mc_down(struct inet6_dev *idev synchronize_net(); mld_query_stop_work(idev); mld_report_stop_work(idev); + + mutex_lock(&idev->mc_lock); mld_ifc_stop_work(idev); mld_gq_stop_work(idev); + mutex_unlock(&idev->mc_lock); + mld_dad_stop_work(idev); }