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Miller" , David Ahern , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Taehee Yoo , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+a9400cabb1d784e49abf@syzkaller.appspotmail.com Subject: Re: [PATCH net] ipv6: mcast: fix data-race in ipv6_mc_down / mld_ifc_work Message-ID: References: <20240117172102.12001-1-n.zhandarovich@fintech.ru> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240117172102.12001-1-n.zhandarovich@fintech.ru> On Wed, Jan 17, 2024 at 09:21:02AM -0800, Nikita Zhandarovich wrote: > 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 > --- > net/ipv6/mcast.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c > index b75d3c9d41bb..bc6e0a0bad3c 100644 > --- a/net/ipv6/mcast.c > +++ b/net/ipv6/mcast.c > @@ -2722,8 +2722,12 @@ 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); > } > I saw mld_process_v1() also cancel these works when changing to v1 mode. Should we also add lock there? Thanks Hangbin