From 4b4b84468aa27d0a18be8cb727f246aa35a3406d Mon Sep 17 00:00:00 2001 From: Taehee Yoo Date: Sun, 4 Apr 2021 13:38:23 +0000 Subject: mld: change lockdep annotation for ip6_sf_socklist and ipv6_mc_socklist 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: 88e2ca308094 ("mld: convert ifmcaddr6 to RCU") Reported-by: Eric Dumazet Signed-off-by: Taehee Yoo Signed-off-by: David S. Miller --- net/tipc/udp_media.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'net/tipc') diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c index 21e75e28e86a..e556d2cdc064 100644 --- a/net/tipc/udp_media.c +++ b/net/tipc/udp_media.c @@ -414,8 +414,10 @@ static int enable_mcast(struct udp_bearer *ub, struct udp_media_addr *remote) err = ip_mc_join_group(sk, &mreqn); #if IS_ENABLED(CONFIG_IPV6) } else { + lock_sock(sk); err = ipv6_stub->ipv6_sock_mc_join(sk, ub->ifindex, &remote->ipv6); + release_sock(sk); #endif } return err; -- cgit v1.2.3