This is a note to let you know that I've just added the patch titled
ipv6: mcast: fix data-race in ipv6_mc_down / mld_ifc_work
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ipv6-mcast-fix-data-race-in-ipv6_mc_down-mld_ifc_wor.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit bf6a916ae296ec5bec77fff52144e43c95594633
Author: Nikita Zhandarovich <n.zhandarovich@xxxxxxxxxx>
Date: Wed Jan 17 09:21:02 2024 -0800
ipv6: mcast: fix data-race in ipv6_mc_down / mld_ifc_work
[ 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@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/000000000000994e09060ebcdffb@xxxxxxxxxx/
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@xxxxxxxxxx>
Acked-by: Taehee Yoo <ap420073@xxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Hangbin Liu <liuhangbin@xxxxxxxxx>
Link: https://lore.kernel.org/r/20240117172102.12001-1-n.zhandarovich@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 7860383295d8..566f3b7b957e 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);
}
