5.15-stable review patch. If anyone has any objections, please let me know.
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From: Nikita Zhandarovich n.zhandarovich@fintech.ru
[ Upstream commit 2e7ef287f07c74985f1bf2858bedc62bd9ebf155 ]
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 n.zhandarovich@fintech.ru Acked-by: Taehee Yoo ap420073@gmail.com Reviewed-by: Eric Dumazet edumazet@google.com Reviewed-by: Hangbin Liu liuhangbin@gmail.com Link: https://lore.kernel.org/r/20240117172102.12001-1-n.zhandarovich@fintech.ru Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv6/mcast.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c index 87c699d57b36..0ea7d97cdc02 100644 --- a/net/ipv6/mcast.c +++ b/net/ipv6/mcast.c @@ -2725,8 +2725,12 @@ 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); }