This is a note to let you know that I've just added the patch titled ipv4: Silence suspicious RCU usage warning to the 5.8-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: ipv4-silence-suspicious-rcu-usage-warning.patch and it can be found in the queue-5.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Fri Sep 11 09:06:45 AM CEST 2020 From: Ido Schimmel <idosch@xxxxxxxxxx> Date: Wed, 26 Aug 2020 19:48:10 +0300 Subject: ipv4: Silence suspicious RCU usage warning From: Ido Schimmel <idosch@xxxxxxxxxx> [ Upstream commit 7f6f32bb7d3355cd78ebf1dece9a6ea7a0ca8158 ] fib_info_notify_update() is always called with RTNL held, but not from an RCU read-side critical section. This leads to the following warning [1] when the FIB table list is traversed with hlist_for_each_entry_rcu(), but without a proper lockdep expression. Since modification of the list is protected by RTNL, silence the warning by adding a lockdep expression which verifies RTNL is held. [1] ============================= WARNING: suspicious RCU usage 5.9.0-rc1-custom-14233-g2f26e122d62f #129 Not tainted ----------------------------- net/ipv4/fib_trie.c:2124 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by ip/834: #0: ffffffff85a3b6b0 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x49a/0xbd0 stack backtrace: CPU: 0 PID: 834 Comm: ip Not tainted 5.9.0-rc1-custom-14233-g2f26e122d62f #129 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-2.fc32 04/01/2014 Call Trace: dump_stack+0x100/0x184 lockdep_rcu_suspicious+0x143/0x14d fib_info_notify_update+0x8d1/0xa60 __nexthop_replace_notify+0xd2/0x290 rtm_new_nexthop+0x35e2/0x5946 rtnetlink_rcv_msg+0x4f7/0xbd0 netlink_rcv_skb+0x17a/0x480 rtnetlink_rcv+0x22/0x30 netlink_unicast+0x5ae/0x890 netlink_sendmsg+0x98a/0xf40 ____sys_sendmsg+0x879/0xa00 ___sys_sendmsg+0x122/0x190 __sys_sendmsg+0x103/0x1d0 __x64_sys_sendmsg+0x7d/0xb0 do_syscall_64+0x32/0x50 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fde28c3be57 Code: 0c 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 89 54 24 1c 48 89 74 24 10 RSP: 002b:00007ffc09330028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fde28c3be57 RDX: 0000000000000000 RSI: 00007ffc09330090 RDI: 0000000000000003 RBP: 000000005f45f911 R08: 0000000000000001 R09: 00007ffc0933012c R10: 0000000000000076 R11: 0000000000000246 R12: 0000000000000001 R13: 00007ffc09330290 R14: 00007ffc09330eee R15: 00005610e48ed020 Fixes: 1bff1a0c9bbd ("ipv4: Add function to send route updates") Signed-off-by: Ido Schimmel <idosch@xxxxxxxxxx> Reviewed-by: David Ahern <dsahern@xxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/ipv4/fib_trie.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -2121,7 +2121,8 @@ void fib_info_notify_update(struct net * struct hlist_head *head = &net->ipv4.fib_table_hash[h]; struct fib_table *tb; - hlist_for_each_entry_rcu(tb, head, tb_hlist) + hlist_for_each_entry_rcu(tb, head, tb_hlist, + lockdep_rtnl_is_held()) __fib_info_notify_update(net, tb, info); } } Patches currently in stable-queue which might be from idosch@xxxxxxxxxx are queue-5.8/ipv4-silence-suspicious-rcu-usage-warning.patch queue-5.8/ipv6-fix-sysctl-max-for-fib_multipath_hash_policy.patch