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4b4b84468a
struct ip6_sf_socklist and ipv6_mc_socklist are per-socket MLD data.
These data are protected by rtnl lock, socket lock, and RCU.
So, when these are used, it verifies whether rtnl lock is acquired or not.
ip6_mc_msfget() is called by do_ipv6_getsockopt().
But caller doesn't acquire rtnl lock.
So, when these data are used in the ip6_mc_msfget() lockdep warns about it.
But accessing these is actually safe because socket lock was acquired by
do_ipv6_getsockopt().
So, it changes lockdep annotation from rtnl lock to socket lock.
(rtnl_dereference -> sock_dereference)
Locking graph for mld data is like below:
When writing mld data:
do_ipv6_setsockopt()
rtnl_lock
lock_sock
(mld functions)
idev->mc_lock(if per-interface mld data is modified)
When reading mld data:
do_ipv6_getsockopt()
lock_sock
ip6_mc_msfget()
Splat looks like:
=============================
WARNING: suspicious RCU usage
5.12.0-rc4+ #503 Not tainted
-----------------------------
net/ipv6/mcast.c:610 suspicious rcu_dereference_protected() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
1 lock held by mcast-listener-/923:
#0: ffff888007958a70 (sk_lock-AF_INET6){+.+.}-{0:0}, at:
ipv6_get_msfilter+0xaf/0x190
stack backtrace:
CPU: 1 PID: 923 Comm: mcast-listener- Not tainted 5.12.0-rc4+ #503
Call Trace:
dump_stack+0xa4/0xe5
ip6_mc_msfget+0x553/0x6c0
? ipv6_sock_mc_join_ssm+0x10/0x10
? lockdep_hardirqs_on_prepare+0x3e0/0x3e0
? mark_held_locks+0xb7/0x120
? lockdep_hardirqs_on_prepare+0x27c/0x3e0
? __local_bh_enable_ip+0xa5/0xf0
? lock_sock_nested+0x82/0xf0
ipv6_get_msfilter+0xc3/0x190
? compat_ipv6_get_msfilter+0x300/0x300
? lock_downgrade+0x690/0x690
do_ipv6_getsockopt.isra.6.constprop.13+0x1809/0x29e0
? do_ipv6_mcast_group_source+0x150/0x150
? register_lock_class+0x1750/0x1750
? kvm_sched_clock_read+0x14/0x30
? sched_clock+0x5/0x10
? sched_clock_cpu+0x18/0x170
? find_held_lock+0x3a/0x1c0
? lock_downgrade+0x690/0x690
? ipv6_getsockopt+0xdb/0x1b0
ipv6_getsockopt+0xdb/0x1b0
[ ... ]
Fixes:
|
||
---|---|---|
.. | ||
6lowpan | ||
9p | ||
802 | ||
8021q | ||
appletalk | ||
atm | ||
ax25 | ||
batman-adv | ||
bluetooth | ||
bpf | ||
bpfilter | ||
bridge | ||
caif | ||
can | ||
ceph | ||
core | ||
dcb | ||
dccp | ||
decnet | ||
dns_resolver | ||
dsa | ||
ethernet | ||
ethtool | ||
hsr | ||
ieee802154 | ||
ife | ||
ipv4 | ||
ipv6 | ||
iucv | ||
kcm | ||
key | ||
l2tp | ||
l3mdev | ||
lapb | ||
llc | ||
mac80211 | ||
mac802154 | ||
mpls | ||
mptcp | ||
ncsi | ||
netfilter | ||
netlabel | ||
netlink | ||
netrom | ||
nfc | ||
nsh | ||
openvswitch | ||
packet | ||
phonet | ||
psample | ||
qrtr | ||
rds | ||
rfkill | ||
rose | ||
rxrpc | ||
sched | ||
sctp | ||
smc | ||
strparser | ||
sunrpc | ||
switchdev | ||
tipc | ||
tls | ||
unix | ||
vmw_vsock | ||
wireless | ||
x25 | ||
xdp | ||
xfrm | ||
compat.c | ||
devres.c | ||
Kconfig | ||
Makefile | ||
socket.c | ||
sysctl_net.c |