netdev - [PATCH net] nfp: fix rcu_read_lock/unlock while rcu

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Message-Id: <20230509060632.8233-1-louis.peens@corigine.com>
Date: Tue,  9 May 2023 08:06:32 +0200
From: Louis Peens <louis.peens@...igine.com>
To: David Miller <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <simon.horman@...igine.com>,
	netdev@...r.kernel.org,
	stable@...r.kernel.org,
	oss-drivers@...igine.com
Subject: [PATCH net] nfp: fix rcu_read_lock/unlock while rcu_derefrencing

From: Tianyu Yuan <tianyu.yuan@...igine.com>

When CONFIG_PROVE_LOCKING and CONFIG_PROVE_RCU are enabled, using
OVS with vf reprs on bridge will lead to following log in dmesg:

'''
 .../nfp/flower/main.c:269 suspicious rcu_dereference_check() usage!

 other info that might help us debug this:

 rcu_scheduler_active = 2, debug_locks = 1
 no locks held by swapper/15/0.

 ......
 Call Trace:
  <IRQ>
  dump_stack_lvl+0x8c/0xa0
  lockdep_rcu_suspicious+0x118/0x1a0
  nfp_flower_dev_get+0xc1/0x240 [nfp]
  nfp_nfd3_rx+0x419/0xb90 [nfp]
  ? validate_chain+0x640/0x1880
  nfp_nfd3_poll+0x3e/0x180 [nfp]
  __napi_poll+0x28/0x1d0
  net_rx_action+0x2bd/0x3c0
  ? _raw_spin_unlock_irqrestore+0x42/0x70
  __do_softirq+0xc3/0x3c6
  irq_exit_rcu+0xeb/0x130
  common_interrupt+0xb9/0xd0
  </IRQ>
  <TASK>
  ......
  </TASK>
'''

This debug log is caused by missing of rcu_read_lock()/unlock().
In previous patch rcu_read_lock/unlock are removed while they are
still needed when calling rcu_dereference() in nfp_app_dev_get().

Fixes: d5789621b658 ("nfp: Remove rcu_read_lock() around XDP program invocation")
CC: stable@...r.kernel.org
Signed-off-by: Tianyu Yuan <tianyu.yuan@...igine.com>
Acked-by: Simon Horman <simon.horman@...igine.com>
Signed-off-by: Louis Peens <louis.peens@...igine.com>
---
 drivers/net/ethernet/netronome/nfp/nfd3/dp.c  |  4 ++--
 drivers/net/ethernet/netronome/nfp/nfd3/xsk.c |  2 +-
 drivers/net/ethernet/netronome/nfp/nfdk/dp.c  |  4 ++--
 drivers/net/ethernet/netronome/nfp/nfp_app.h  | 16 ++++++++++++++++
 4 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfd3/dp.c b/drivers/net/ethernet/netronome/nfp/nfd3/dp.c
index 0cc026b0aefd..3e5a84370d8a 100644
--- a/drivers/net/ethernet/netronome/nfp/nfd3/dp.c
+++ b/drivers/net/ethernet/netronome/nfp/nfd3/dp.c
@@ -1058,8 +1058,8 @@ static int nfp_nfd3_rx(struct nfp_net_rx_ring *rx_ring, int budget)
 			struct nfp_net *nn;
 
 			nn = netdev_priv(dp->netdev);
-			netdev = nfp_app_dev_get(nn->app, meta.portid,
-						 &redir_egress);
+			netdev = nfp_app_dev_get_locked(nn->app, meta.portid,
+							&redir_egress);
 			if (unlikely(!netdev)) {
 				nfp_nfd3_rx_drop(dp, r_vec, rx_ring, rxbuf,
 						 NULL);
diff --git a/drivers/net/ethernet/netronome/nfp/nfd3/xsk.c b/drivers/net/ethernet/netronome/nfp/nfd3/xsk.c
index 5d9db8c2a5b4..6ec5b0d430ea 100644
--- a/drivers/net/ethernet/netronome/nfp/nfd3/xsk.c
+++ b/drivers/net/ethernet/netronome/nfp/nfd3/xsk.c
@@ -71,7 +71,7 @@ static void nfp_nfd3_xsk_rx_skb(struct nfp_net_rx_ring *rx_ring,
 	} else {
 		struct nfp_net *nn = netdev_priv(dp->netdev);
 
-		netdev = nfp_app_dev_get(nn->app, meta->portid, NULL);
+		netdev = nfp_app_dev_get_locked(nn->app, meta->portid, NULL);
 		if (unlikely(!netdev)) {
 			nfp_net_xsk_rx_drop(r_vec, xrxbuf);
 			return;
diff --git a/drivers/net/ethernet/netronome/nfp/nfdk/dp.c b/drivers/net/ethernet/netronome/nfp/nfdk/dp.c
index 33b6d74adb4b..0ac68985d289 100644
--- a/drivers/net/ethernet/netronome/nfp/nfdk/dp.c
+++ b/drivers/net/ethernet/netronome/nfp/nfdk/dp.c
@@ -1177,8 +1177,8 @@ static int nfp_nfdk_rx(struct nfp_net_rx_ring *rx_ring, int budget)
 			struct nfp_net *nn;
 
 			nn = netdev_priv(dp->netdev);
-			netdev = nfp_app_dev_get(nn->app, meta.portid,
-						 &redir_egress);
+			netdev = nfp_app_dev_get_locked(nn->app, meta.portid,
+							&redir_egress);
 			if (unlikely(!netdev)) {
 				nfp_nfdk_rx_drop(dp, r_vec, rx_ring, rxbuf,
 						 NULL);
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_app.h b/drivers/net/ethernet/netronome/nfp/nfp_app.h
index 90707346a4ef..639bb1a6349b 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_app.h
+++ b/drivers/net/ethernet/netronome/nfp/nfp_app.h
@@ -417,6 +417,22 @@ struct net_device *nfp_app_dev_get(struct nfp_app *app, u32 id,
 	return app->type->dev_get(app, id, redir_egress);
 }
 
+static inline
+struct net_device *nfp_app_dev_get_locked(struct nfp_app *app, u32 id,
+					  bool *redir_egress)
+{
+	struct net_device *dev;
+
+	if (unlikely(!app || !app->type->dev_get))
+		return NULL;
+
+	rcu_read_lock();
+	dev = app->type->dev_get(app, id, redir_egress);
+	rcu_read_unlock();
+
+	return dev;
+}
+
 struct nfp_app *nfp_app_from_netdev(struct net_device *netdev);
 
 u64 *nfp_app_port_get_stats(struct nfp_port *port, u64 *data);
-- 
2.34.1