This is a note to let you know that I've just added the patch titled netfilter: ctnetlink: suspicious RCU usage in ctnetlink_dump_helpinfo to the 4.14-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: netfilter-ctnetlink-suspicious-rcu-usage-in-ctnetlink_dump_helpinfo.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From c23a9fd209bc6f8c1fa6ee303fdf037d784a1627 Mon Sep 17 00:00:00 2001 From: Vasily Averin <vvs@xxxxxxxxxxxxx> Date: Thu, 1 Jul 2021 08:02:49 +0300 Subject: netfilter: ctnetlink: suspicious RCU usage in ctnetlink_dump_helpinfo From: Vasily Averin <vvs@xxxxxxxxxxxxx> commit c23a9fd209bc6f8c1fa6ee303fdf037d784a1627 upstream. Two patches listed below removed ctnetlink_dump_helpinfo call from under rcu_read_lock. Now its rcu_dereference generates following warning: ============================= WARNING: suspicious RCU usage 5.13.0+ #5 Not tainted ----------------------------- net/netfilter/nf_conntrack_netlink.c:221 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 stack backtrace: CPU: 1 PID: 2251 Comm: conntrack Not tainted 5.13.0+ #5 Call Trace: dump_stack+0x7f/0xa1 ctnetlink_dump_helpinfo+0x134/0x150 [nf_conntrack_netlink] ctnetlink_fill_info+0x2c2/0x390 [nf_conntrack_netlink] ctnetlink_dump_table+0x13f/0x370 [nf_conntrack_netlink] netlink_dump+0x10c/0x370 __netlink_dump_start+0x1a7/0x260 ctnetlink_get_conntrack+0x1e5/0x250 [nf_conntrack_netlink] nfnetlink_rcv_msg+0x613/0x993 [nfnetlink] netlink_rcv_skb+0x50/0x100 nfnetlink_rcv+0x55/0x120 [nfnetlink] netlink_unicast+0x181/0x260 netlink_sendmsg+0x23f/0x460 sock_sendmsg+0x5b/0x60 __sys_sendto+0xf1/0x160 __x64_sys_sendto+0x24/0x30 do_syscall_64+0x36/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xae Fixes: 49ca022bccc5 ("netfilter: ctnetlink: don't dump ct extensions of unconfirmed conntracks") Fixes: 0b35f6031a00 ("netfilter: Remove duplicated rcu_read_lock.") Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx> Reviewed-by: Florian Westphal <fw@xxxxxxxxx> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/netfilter/nf_conntrack_netlink.c | 3 +++ 1 file changed, 3 insertions(+) --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -196,6 +196,7 @@ static int ctnetlink_dump_helpinfo(struc if (!help) return 0; + rcu_read_lock(); helper = rcu_dereference(help->helper); if (!helper) goto out; @@ -211,9 +212,11 @@ static int ctnetlink_dump_helpinfo(struc nla_nest_end(skb, nest_helper); out: + rcu_read_unlock(); return 0; nla_put_failure: + rcu_read_unlock(); return -1; } Patches currently in stable-queue which might be from vvs@xxxxxxxxxxxxx are queue-4.14/netfilter-ctnetlink-suspicious-rcu-usage-in-ctnetlink_dump_helpinfo.patch