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_init_flow()
to the 6.6-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-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit fbb3bc8ed535838660fafbbfe132f2ab103a3e87
Author: Ido Schimmel <idosch@xxxxxxxxxx>
Date: Tue Oct 22 09:38:22 2024 +0300
ipv4: ip_tunnel: Fix suspicious RCU usage warning in ip_tunnel_init_flow()
[ Upstream commit ad4a3ca6a8e886f6491910a3ae5d53595e40597d ]
There are code paths from which the function is called without holding
the RCU read lock, resulting in a suspicious RCU usage warning [1].
Fix by using l3mdev_master_upper_ifindex_by_index() which will acquire
the RCU read lock before calling
l3mdev_master_upper_ifindex_by_index_rcu().
[1]
WARNING: suspicious RCU usage
6.12.0-rc3-custom-gac8f72681cf2 #141 Not tainted
-----------------------------
net/core/dev.c:876 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/361:
#0: ffffffff86fc7cb0 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x377/0xf60
stack backtrace:
CPU: 3 UID: 0 PID: 361 Comm: ip Not tainted 6.12.0-rc3-custom-gac8f72681cf2 #141
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Call Trace:
<TASK>
dump_stack_lvl+0xba/0x110
lockdep_rcu_suspicious.cold+0x4f/0xd6
dev_get_by_index_rcu+0x1d3/0x210
l3mdev_master_upper_ifindex_by_index_rcu+0x2b/0xf0
ip_tunnel_bind_dev+0x72f/0xa00
ip_tunnel_newlink+0x368/0x7a0
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: db53cd3d88dc ("net: Handle l3mdev in ip_tunnel_init_flow")
Signed-off-by: Ido Schimmel <idosch@xxxxxxxxxx>
Reviewed-by: David Ahern <dsahern@xxxxxxxxxx>
Link: https://patch.msgid.link/20241022063822.462057-1-idosch@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
index 4e69f52a51177..006a61ddd36fa 100644
--- a/include/net/ip_tunnels.h
+++ b/include/net/ip_tunnels.h
@@ -260,7 +260,7 @@ static inline void ip_tunnel_init_flow(struct flowi4 *fl4,
memset(fl4, 0, sizeof(*fl4));
if (oif) {
- fl4->flowi4_l3mdev = l3mdev_master_upper_ifindex_by_index_rcu(net, oif);
+ fl4->flowi4_l3mdev = l3mdev_master_upper_ifindex_by_index(net, oif);
/* Legacy VRF/l3mdev use case */
fl4->flowi4_oif = fl4->flowi4_l3mdev ? 0 : oif;
}
