From: Ido Schimmel idosch@nvidia.com

commit 90e0569dd3d32f4f4d2ca691d3fa5a8a14a13c12 upstream.

The per-netns IP tunnel hash table is protected by the RTNL mutex and ip_tunnel_find() is only called from the control path where the mutex is taken.

Add a lockdep expression to hlist_for_each_entry_rcu() in ip_tunnel_find() in order to validate that the mutex is held and to silence the suspicious RCU usage warning [1].

[1] WARNING: suspicious RCU usage 6.12.0-rc3-custom-gd95d9a31aceb #139 Not tainted ----------------------------- net/ipv4/ip_tunnel.c:221 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/362: #0: ffffffff86fc7cb0 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x377/0xf60

stack backtrace: CPU: 12 UID: 0 PID: 362 Comm: ip Not tainted 6.12.0-rc3-custom-gd95d9a31aceb #139 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Call Trace: <TASK> dump_stack_lvl+0xba/0x110 lockdep_rcu_suspicious.cold+0x4f/0xd6 ip_tunnel_find+0x435/0x4d0 ip_tunnel_newlink+0x517/0x7a0 ipgre_newlink+0x14c/0x170 __rtnl_newlink+0x1173/0x19c0 rtnl_newlink+0x6c/0xa0 rtnetlink_rcv_msg+0x3cc/0xf60 netlink_rcv_skb+0x171/0x450 netlink_unicast+0x539/0x7f0 netlink_sendmsg+0x8c1/0xd80 ____sys_sendmsg+0x8f9/0xc20 ___sys_sendmsg+0x197/0x1e0 __sys_sendmsg+0x122/0x1f0 do_syscall_64+0xbb/0x1d0 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fixes: c54419321455 ("GRE: Refactor GRE tunneling code.") Suggested-by: Eric Dumazet edumazet@google.com Signed-off-by: Ido Schimmel idosch@nvidia.com Reviewed-by: Eric Dumazet edumazet@google.com Link: https://patch.msgid.link/20241023123009.749764-1-idosch@nvidia.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Alva Lan alvalan9@foxmail.com --- net/ipv4/ip_tunnel.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c index dd1803bf9c5c..b5d64cd3ab0a 100644 --- a/net/ipv4/ip_tunnel.c +++ b/net/ipv4/ip_tunnel.c @@ -218,7 +218,7 @@ static struct ip_tunnel *ip_tunnel_find(struct ip_tunnel_net *itn, struct ip_tunnel *t = NULL; struct hlist_head *head = ip_bucket(itn, parms);

- hlist_for_each_entry_rcu(t, head, hash_node) { + hlist_for_each_entry_rcu(t, head, hash_node, lockdep_rtnl_is_held()) { if (local == t->parms.iph.saddr && remote == t->parms.iph.daddr && link == READ_ONCE(t->parms.link) &&