[PATCH 4.4 073/188] vxlan: add missing rcu_read_lock() in neigh_reduce()

Greg Kroah-Hartman
2021-07-19T15:01:56Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 85e8b032d6ebb0f698a34dd22c2f13443d905888 ]

syzbot complained in neigh_reduce(), because rcu_read_lock_bh()
is treated differently than rcu_read_lock()

WARNING: suspicious RCU usage
5.13.0-rc6-syzkaller #0 Not tainted
-----------------------------
include/net/addrconf.h:313 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
3 locks held by kworker/0:0/5:
#0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
#0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
#0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:617 [inline]
#0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
#0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x871/0x1600 kernel/workqueue.c:2247
#1: ffffc90000ca7da8 ((work_completion)(&port->wq)){+.+.}-{0:0}, at: process_one_work+0x8a5/0x1600 kernel/workqueue.c:2251
#2: ffffffff8bf795c0 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x1da/0x3130 net/core/dev.c:4180

stack backtrace:
CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted 5.13.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events ipvlan_process_multicast
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x141/0x1d7 lib/dump_stack.c:120
__in6_dev_get include/net/addrconf.h:313 [inline]
__in6_dev_get include/net/addrconf.h:311 [inline]
neigh_reduce drivers/net/vxlan.c:2167 [inline]
vxlan_xmit+0x34d5/0x4c30 drivers/net/vxlan.c:2919
__netdev_start_xmit include/linux/netdevice.h:4944 [inline]
netdev_start_xmit include/linux/netdevice.h:4958 [inline]
xmit_one net/core/dev.c:3654 [inline]
dev_hard_start_xmit+0x1eb/0x920 net/core/dev.c:3670
__dev_queue_xmit+0x2133/0x3130 net/core/dev.c:4246
ipvlan_process_multicast+0xa99/0xd70 drivers/net/ipvlan/ipvlan_core.c:287
process_one_work+0x98d/0x1600 kernel/workqueue.c:2276
worker_thread+0x64c/0x1120 kernel/workqueue.c:2422
kthread+0x3b1/0x4a0 kernel/kthread.c:313
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Fixes: f564f45c4518 ("vxlan: add ipv6 proxy support")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/vxlan.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 50ede6b8b874..4d44ec5b7cd7 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1549,6 +1549,7 @@ static int neigh_reduce(struct net_device *dev, struct sk_buff *skb)
struct neighbour *n;
struct inet6_dev *in6_dev;

+ rcu_read_lock();
in6_dev = __in6_dev_get(dev);
if (!in6_dev)
goto out;
@@ -1605,6 +1606,7 @@ static int neigh_reduce(struct net_device *dev, struct sk_buff *skb)
}

out:
+ rcu_read_unlock();
consume_skb(skb);
return NETDEV_TX_OK;
}
--
2.30.2