This is a note to let you know that I've just added the patch titled
ipv4: ip_tunnel: Fix suspicious RCU usage warning in ip_tunnel_find()
to the 6.11-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-ip_tunnel-fix-suspicious-rcu-usage-warning-in-i.patch
and it can be found in the queue-6.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f443ccf96415fe21b45445da8b79b00ab612d765
Author: Ido Schimmel <idosch@xxxxxxxxxx>
Date: Wed Oct 23 15:30:09 2024 +0300
ipv4: ip_tunnel: Fix suspicious RCU usage warning in ip_tunnel_find()
[ Upstream commit 90e0569dd3d32f4f4d2ca691d3fa5a8a14a13c12 ]
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@xxxxxxxxxx>
Signed-off-by: Ido Schimmel <idosch@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://patch.msgid.link/20241023123009.749764-1-idosch@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 5cffad42fe8ca..49937878d5e8a 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -217,7 +217,7 @@ static struct ip_tunnel *ip_tunnel_find(struct ip_tunnel_net *itn,
ip_tunnel_flags_copy(flags, parms->i_flags);
- 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) &&
